ANDROID: mm: compaction: fix isolate_and_split_free_page() redefinition

Guard isolate_and_split_free_page() with CONFIG_COMPACTION. This fixes
the follwoing build error as the function collides with its inline stub
from the header file:

mm/compaction.c:766:15: error: redefinition of ‘isolate_and_split_free_page’
  766 | unsigned long isolate_and_split_free_page(struct page *page,
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from mm/compaction.c:14:
./include/linux/compaction.h:241:29: note: previous definition of ‘isolate_and_split_free_page’ was here
  241 | static inline unsigned long isolate_and_split_free_page(struct page *page,
      |                             ^~~~~~~~~~~~~~~~~~~~~~~~~~~

Bug: 201263307
Change-Id: Ie8f3fedcc9d4af5cfdcfd5829377671745ab77d6
Fixes: 8cd9aa93 ("ANDROID: implement wrapper for reverse migration")
Reported-by: kernelci.org bot <bot@kernelci.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Signed-off-by: Sukadev Bhattiprolu <quic_sukadev@quicinc.com>