[XFS] clean up xfs_bmbt_set_all/xfs_bmbt_disk_set_all

xfs_bmbt_set_all/xfs_bmbt_disk_set_all are identical to
xfs_bmbt_set_allf/xfs_bmbt_disk_set_allf except that the former take a
xfs_bmbt_irec_t and the latter take the individual extent fields as scalar
values.

This patch reimplements xfs_bmbt_set_all/xfs_bmbt_disk_set_all as trivial
wrappers around xfs_bmbt_set_allf/xfs_bmbt_disk_set_allf and cleans up the
variable naming in xfs_bmbt_set_allf/xfs_bmbt_disk_set_allf to have some
meaning instead of one char variable names.

SGI-PV: 968563
SGI-Modid: xfs-linux-melb:xfs-kern:29319a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>