[XFS] kill t_sema member of struct xfs_trans

It's completely unused so we might aswell kill it. Note that there is
another t_sema in struct xlog_ticket, which is used and actually an sv_t
despite the name. That one is left untouched by this patch.

SGI-PV: 971186
SGI-Modid: xfs-linux-melb:xfs-kern:30591a
Signed-off-by: NNiv Sardi <xaiki@sgi.com>
Signed-off-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NLachlan McIlroy <lachlan@sgi.com>

fs/xfs/xfs_trans.h

@@ -341,7 +341,6 @@ typedef struct xfs_trans {
 	unsigned int		t_rtx_res;	/* # of rt extents resvd */
 	unsigned int		t_rtx_res_used;	/* # of resvd rt extents used */
 	xfs_log_ticket_t	t_ticket;	/* log mgr ticket */
-	sema_t			t_sema;		/* sema for commit completion */
 	xfs_lsn_t		t_lsn;		/* log seq num of start of
 						 * transaction. */
 	xfs_lsn_t		t_commit_lsn;	/* log seq num of end of