cpu-arm: Fix incorrect free

A bug was introduced with the refactoring in da26563a. In arm_init, the buffer passed to spa_cpu_read_file is allocated and it is just going to return that. So cpuinfo will actually point to buffer on the stack, which need not be freed with a call to free.

The crash resulting with the incorrect free.

root@dragonboard-845c:~# pipewire --version
munmap_chunk(): invalid pointer
[  185.037284] audit: type=1701 audit(1659949975.843:14): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=2243 comm="pipewire" exe="/usr/bin/pipewire" sig=6 res=1
Aborted
root@dragonboard-845c:~# wireplumber --version
munmap_chunk(): invalid pointer
[  193.453693] audit: type=1701 audit(1659949984.255:15): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=2244 comm="wireplumber" exe="/usr/bin/wireplumber" sig=6 res=1
Aborted

Backtrace from the crash

(gdb) bt
!0  __pthread_kill_implementation (threadid=<optimized out>, signo=signo@entry=6, no_tid=no_tid@entry=0) at pthread_kill.c:44
!1  0x0000fffff7d8edd8 in __pthread_kill_internal (signo=6, threadid=<optimized out>) at pthread_kill.c:78
!2  0x0000fffff7d4a390 in __GI_raise (sig=sig@entry=6) at /usr/src/debug/glibc/2.36-r0/sysdeps/posix/raise.c:26
!3  0x0000fffff7d37498 in __GI_abort () at abort.c:79
!4  0x0000fffff7d83374 in __libc_message (action=action@entry=do_abort, fmt=fmt@entry=0xfffff7e5fc20 "%s\n") at /usr/src/debug/glibc/2.36-r0/sysdeps/posix/libc_fatal.c:155
!5  0x0000fffff7d988c0 in malloc_printerr (str=str@entry=0xfffff7e5a7f0 "munmap_chunk(): invalid pointer") at malloc.c:5660
!6  0x0000fffff7d98aac in munmap_chunk (p=p@entry=0xffffffffd258) at malloc.c:3054
!7  0x0000fffff7d9d068 in __GI___libc_free (mem=mem@entry=0xffffffffd268) at malloc.c:3375
!8  0x0000fffff7cd36cc in arm_init (impl=impl@entry=0xaaaaaaac8c48) at /usr/src/debug/pipewire/1.0-r0/spa/plugins/support/cpu-arm.c:97
!9  0x0000fffff7cd391c in impl_init (factory=<optimized out>, handle=0xaaaaaaac8c48, info=0xffffffffe548, support=<optimized out>, n_support=<optimized out>) at /usr/src/debug/pipewire/1.0-r0/spa/plugins/support/cpu.c:264
!10 0x0000fffff7f3a234 in load_spa_handle (lib=<optimized out>, factory_name=factory_name@entry=0xfffff7f6d768 "support.cpu", info=info@entry=0xffffffffe548, n_support=1,
    support=support@entry=0xfffff7fb0488 <global_support+88>) at /usr/src/debug/pipewire/1.0-r0/src/pipewire/pipewire.c:280
!11 0x0000fffff7f3a5b0 in add_interface (factory_name=factory_name@entry=0xfffff7f6d768 "support.cpu", type=type@entry=0xfffff7f62310 "Spa:Pointer:Interface:CPU", info=info@entry=0xffffffffe548,
    support=0xfffff7fb0430 <global_support>) at /usr/src/debug/pipewire/1.0-r0/src/pipewire/pipewire.c:358
!12 0x0000fffff7f3b3f8 in pw_init (argc=argc@entry=0xffffffffea5c, argv=argv@entry=0xffffffffea50) at /usr/src/debug/pipewire/1.0-r0/src/pipewire/pipewire.c:661
!13 0x0000aaaaaaaa1104 in main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/pipewire/1.0-r0/src/daemon/pipewire.c:79
(gdb) f 8
!8  0x0000fffff7cd36cc in arm_init (impl=impl@entry=0xaaaaaaac8c48) at /usr/src/debug/pipewire/1.0-r0/spa/plugins/support/cpu-arm.c:97
97      /usr/src/debug/pipewire/1.0-r0/spa/plugins/support/cpu-arm.c: No such file or directory.
(gdb) info locals
flags = 122
cpuinfo = 0xffffffffd268 "processor\t: 0\nBogoMIPS\t: 38.40\nFeatures\t: fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop\nCPU implementer\t: 0x51\nCPU architecture: 8\nCPU variant\t.
line = 0xaaaaaaac8ce0 "\310\252\252\252\n"
buffer = "processor\t: 0\nBogoMIPS\t: 38.40\nFeatures\t: fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm lrcpc dcpop\nCPU implementer\t: 0x51\nCPU architecture: 8\nCPU variant\t: 0x7\nCPU pa"...
arch = <optimized out>
__func__ = "arm_init"