LoongArch: Add kernel livepatching support

The arch-specified function ftrace_regs_set_instruction_pointer() has
been implemented in arch/loongarch/include/asm/ftrace.h, so here only
implement arch_stack_walk_reliable() function.

Here are the test logs:

[root@linux fedora]# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-6.8.0-rc2 root=/dev/sda3

[root@linux fedora]# modprobe livepatch-sample
[root@linux fedora]# cat /proc/cmdline
this has been live patched

[root@linux fedora]# echo 0 > /sys/kernel/livepatch/livepatch_sample/enabled
[root@linux fedora]# rmmod livepatch_sample
[root@linux fedora]# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-6.8.0-rc2 root=/dev/sda3

[root@linux fedora]# dmesg -t | tail -5
livepatch: enabling patch 'livepatch_sample'
livepatch: 'livepatch_sample': starting patching transition
livepatch: 'livepatch_sample': patching complete
livepatch: 'livepatch_sample': starting unpatching transition
livepatch: 'livepatch_sample': unpatching complete

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>