kfence: fix implicit function declaration

kfence: fix implicit function declaration

When building kfence the following error shows up:

In file included from mm/kfence/report.c:13:
arch/arm64/include/asm/kfence.h: In function `kfence_protect_page':
arch/arm64/include/asm/kfence.h:12:2: error: implicit declaration of function `set_memory_valid' [-Werror=implicit-function-declaration]
   12 |  set_memory_valid(addr, 1, !protect);
      |  ^~~~~~~~~~~~~~~~

Use the correct include both
f2b7c491916d ("set_memory: allow querying whether set_direct_map_*() is actually enabled")
and 4c4c75881536 ("arm64, kfence: enable KFENCE for ARM64") went in the
same day via different trees.

Link: https://lkml.kernel.org/r/20201204121804.1532849-1-anders.roxell@linaro.org
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>