lib/plist.c: enforce memory ordering in plist_check_list

lib/plist.c: enforce memory ordering in plist_check_list

There exists an iteration over a plist in plist_check_list(), and memory
dependency exists between variables "prev", "next" and "prev->next".  As
plist is used in the scheduling subsystem, we should guarantee the memory
ordering between multiple processors.

Using macro "WRITE_ONCE()" can help us to ensure the memory ordering as
it was stated in "Documentation/memory-barriers.txt".

Link: https://lkml.kernel.org/r/20240526140139.17220-1-richard120310@gmail.com
Signed-off-by: I Hsin Cheng <richard120310@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>