MAINTAINERS: Update entries of ext2 and ext3

I often handle ext2 and ext3 patches these days so add myself to MAINTAINERS.

CC: Andrew Morton <akpm@linux-foundation.org>
CC: Andreas Dilger <andreas.dilger@oracle.com>
CC: linux-ext4@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>

MAINTAINERS

@@ -2222,13 +2222,15 @@ S:	Maintained
 F:	drivers/net/eth16i.c
 
 EXT2 FILE SYSTEM
+M:	Jan Kara <jack@suse.cz>
 L:	linux-ext4@vger.kernel.org
 S:	Maintained
 F:	Documentation/filesystems/ext2.txt
 F:	fs/ext2/
 F:	include/linux/ext2*
 
 EXT3 FILE SYSTEM
+M:	Jan Kara <jack@suse.cz>
 M:	Andrew Morton <akpm@linux-foundation.org>
 M:	Andreas Dilger <adilger.kernel@dilger.ca>
 L:	linux-ext4@vger.kernel.org