xfs: drop fop_flags for directories

Directories have non of the capabilities, so drop the flags.  Note that
the current state is harmless as no one actually checks for the flags
either.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240423124608.537794-3-hch@lst.de


Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>