xfs: hoist freeing of rt data fork extent mappings

[ Upstream commit 6c664484 ]

Currently, xfs_bmap_del_extent_real contains a bunch of code to convert
the physical extent of a data fork mapping for a realtime file into rt
extents and pass that to the rt extent freeing function.  Since the
details of this aren't needed when CONFIG_XFS_REALTIME=n, move it to
xfs_rtbitmap.c to reduce code size when realtime isn't enabled.

This will (one day) enable realtime EFIs to reuse the same
unit-converting call with less code duplication.

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>