xfs: rt stubs should return negative errnos when rt disabled

[ Upstream commit c2988eb5 ]

When realtime support is not compiled into the kernel, these functions
should return negative errnos, not positive errnos.  While we're at it,
fix a broken macro declaration.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>