f2fs: update Kconfig and Makefile

This adds Makefile and Kconfig for f2fs, and updates Makefile and Kconfig files
in the fs directory.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/Kconfig

@@ -220,6 +220,7 @@ source "fs/pstore/Kconfig"
 source "fs/sysv/Kconfig"
 source "fs/ufs/Kconfig"
 source "fs/exofs/Kconfig"
+source "fs/f2fs/Kconfig"
 
 endif # MISC_FILESYSTEMS