scripts/checkstack.pl: fix no space expression between sp and offset

When I use older version aarch64 objdump (2.24) to disassemble aarch64
vmlinux, I get the result like below.  There is no space between sp and
offset.

ffff800008010000 <dw_apb_ictl_handle_irq>:
ffff800008010000:       d503233f        hint    #0x19
ffff800008010004:       a9bc7bfd        stp     x29, x30, [sp,#-64]!
ffff800008010008:       90011e60        adrp    x0, ffff80000a3dc000 <num_ictlrs>
ffff80000801000c:       910003fd        mov     x29, sp
ffff800008010010:       a9025bf5        stp     x21, x22, [sp,#32]

When I use newer version aarch64 objdump (2.35), I get
the result like below.
There is a space between sp and offset.

ffff800008010000 <dw_apb_ictl_handle_irq>:
ffff800008010000:       d503233f        paciasp
ffff800008010004:       a9bc7bfd        stp     x29, x30, [sp, #-64]!
ffff800008010008:       90011e60        adrp    x0, ffff80000a3dc000 <num_ictlrs>
ffff80000801000c:       910003fd        mov     x29, sp
ffff800008010010:       a9025bf5        stp     x21, x22, [sp, #32]

Add no space support of regular expression for old version objdump.

Link: https://lkml.kernel.org/r/20231220073629.2658-1-Kuan-Ying.Lee@mediatek.com


Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: Casper Li <casper.li@mediatek.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Qun-Wei Lin <qun-wei.lin@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>