xfs: kill the unused xlog_debug variable

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 5b72e9a..7fc2c8d 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -201,9 +201,4 @@
 bool	xfs_log_item_in_current_chkpt(struct xfs_log_item *lip);
 
 #endif
-
-
-extern int xlog_debug;		/* set to 1 to enable real log */
-
-
 #endif	/* __XFS_LOG_H__ */