fs: add native exFAT support (Samsung OSRC 1.2.4)

http://opensource.samsung.com/reception/receptionSub.do?method=sub&sub=F&searchValue=exfat

Change-Id: I800e6bbd95da3ff68c4234a1f45a6571546c1451
Update to exFAT 1.2.5

Change-Id: I2b1379980baa1b4ff69ae84093c190b1f7b69208
golden: add exFAT config