fs: ext2: Fix duplicate included linux/dax.h

Clean up the following includecheck warning:

fs/ext2/inode.c: linux/dax.h is included more than once.

No functional change.
Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/1648008123-32485-1-git-send-email-baihaowen@meizu.com

fs/ext2/inode.c

@@ -36,7 +36,6 @@
 #include <linux/iomap.h>
 #include <linux/namei.h>
 #include <linux/uio.h>
-#include <linux/dax.h>
 #include "ext2.h"
 #include "acl.h"
 #include "xattr.h"