MAINTAINERS: change the email address for f2fs

This patch changes the valid email address to maintain the f2fs file system.
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

MAINTAINERS

@@ -3774,7 +3774,7 @@ F:	fs/fscache/
 F:	include/linux/fscache*.h
 
 F2FS FILE SYSTEM
-M:	Jaegeuk Kim <jaegeuk.kim@samsung.com>
+M:	Jaegeuk Kim <jaegeuk@kernel.org>
 L:	linux-f2fs-devel@lists.sourceforge.net
 W:	http://en.wikipedia.org/wiki/F2FS
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git