fat already uses synchronous discards, no need to add I/O barriers.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: linux-2.6/fs/fat/fatent.c
===================================================================
--- linux-2.6.orig/fs/fat/fatent.c	2010-08-17 16:49:12.976253898 +0200
+++ linux-2.6/fs/fat/fatent.c	2010-08-17 16:49:17.378285050 +0200
@@ -579,7 +579,7 @@ int fat_free_clusters(struct inode *inod
 					fat_clus_to_blknr(sbi, first_cl),
 					nr_clus * sbi->sec_per_clus,
 					GFP_NOFS,
-					BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
+					BLKDEV_IFL_WAIT);
 
 				first_cl = cluster;
 			}