fs: Update exFAT to version 1.2.7 (Samsung OSRC from KK sources)

Change-Id: Ic4fadf0eaa7ff6b294fa68db1bf1bc3d351f2033
Added optimized ARM RWSEM algorithm.

Change-Id: I340d80a663a7db3ac87f5c33cb21273b14fbeafa
config: enable RWSEM_XCHGADD_ALGORITHM

Change-Id: I5e539832f78ee0cb4127e6b905c4f63a8ad75e97