ext4: Check if inode uses extents in ext4_inode_can_atomic_write()

ext4: Check if inode uses extents in ext4_inode_can_atomic_write()

EXT4 only supports doing atomic write on inodes which uses extents, so
add a check in ext4_inode_can_atomic_write() which gets called during
open.

Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://patch.msgid.link/86bb502c979398a736ab371d8f35f6866a477f6c.1747337952.git.ritesh.list@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>