xfs: rename xfs_inode_can_atomicwrite() -> xfs_inode_can_hw_atomic_write()

In future we will want to be able to check if specifically HW offload-based
atomic writes are possible, so rename xfs_inode_can_atomicwrite() ->
xfs_inode_can_hw_atomicwrite().

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[djwong: add an underscore to be consistent with everything else]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>