ANDROID: GKI: fix up crc issue in crypto_get_default_null_skcipher()

In commit 0486de3c ("crypto: null - Use spin lock instead of
mutex"), the .h files get shuffled around a bit, which causes a CRC
mismatch in crypto_get_default_null_skcipher().  Add back mm.h to the
build to keep the CRC calculations the same.

Bug: 161946584
Fixes: 0486de3c ("crypto: null - Use spin lock instead of mutex")
Change-Id: I7d1490944efbbd3bdc99e4116014b5f32ab3d708
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>