test_firmware: Add test support for firmware upload

Add support for testing the firmware upload driver. There are four sysfs
nodes added:

upload_register: write-only
  Write the name of the firmware device node to be created

upload_unregister: write-only
  Write the name of the firmware device node to be destroyed

config_upload_name: read/write
  Set the name to be used by upload_read

upload_read: read-only
  Read back the data associated with the firmware device node named
  in config_upload_name

You can create multiple, concurrent firmware device nodes for firmware
upload testing. Read firmware back and validate it using config_upload_name
and upload_red.

Example:
    $ cd /sys/devices/virtual/misc/test_firmware
    $ echo -n fw1 > upload_register
    $ ls fw1
    cancel  data  device  error  loading  power  remaining_size  status
    subsystem  uevent
    $ dd if=/dev/urandom of=/tmp/random-firmware.bin bs=512 count=4
    4+0 records in
    4+0 records out
    2048 bytes (2.0 kB, 2.0 KiB) copied, 0.000131959 s, 15.5 MB/s
    $ echo 1 > fw1/loading
    $ cat /tmp/random-firmware.bin > fw1/data
    $ echo 0 > fw1/loading
    $ cat fw1/status
    idle
    $ cat fw1/error
    $ echo -n fw1 > config_upload_name
    $ cmp /tmp/random-firmware.bin upload_read
    $ echo $?
    0
    $ echo -n fw1 > upload_unregister

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Tianfei zhang <tianfei.zhang@intel.com>
Tested-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Link: https://lore.kernel.org/r/20220421212204.36052-7-russell.h.weight@intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>