mm: kmsan: remove runtime checks from kmsan_unpoison_memory()

Similarly to what's been done in commit 85716a80 ("kmsan: allow using
__msan_instrument_asm_store() inside runtime"), it should be safe to call
kmsan_unpoison_memory() from within the runtime, as it does not allocate
memory or take locks.  Remove the redundant runtime checks.

This should fix false positives seen with CONFIG_DEBUG_LIST=y when
the non-instrumented lib/stackdepot.c failed to unpoison the memory
chunks later checked by the instrumented lib/list_debug.c

Also replace the implementation of kmsan_unpoison_entry_regs() with
a call to kmsan_unpoison_memory().

Link: https://lkml.kernel.org/r/20240124173134.1165747-1-glider@google.com


Fixes: f80be457 ("kmsan: add KMSAN runtime core")
Signed-off-by: Alexander Potapenko <glider@google.com>
Tested-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Nicholas Miehlbradt <nicholas@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>