ANDROID: mm: fix build break

MIGRATE_CMA is defined only when CONFIG_CMA. Thus, we
couldn't use MIGRATE_CMA directly to build for both
!CONFIG_CMA and CONFIG_CMA.

Let's use MIGRATE_RECLAIMABLE in the case.

Bug: 218731671
Signed-off-by: Minchan Kim <minchan@google.com>
Change-Id: Idb4fc6f4ea02ab074f270ce62001182c8fff3b37