xfs: IOMAP_ZERO and IOMAP_UNSHARE already hold invalidate_lock

All XFS callers of iomap_zero_range and iomap_file_unshare already hold
invalidate_lock, so we can't take it again in
iomap_file_buffered_write_punch_delalloc.

Use the passed in flags argument to detect if we're called from a zero
or unshare operation and don't take the lock again in this case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>