[XFS] standardize on one sema init macro

One sema to rule them all, one sema to find them...

SGI-PV: 907752
SGI-Modid: xfs-linux-melb:xfs-kern:26911a

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>