xenlinux: disable blkback barriers

It is broken connected with pvops frontend

patches.xen/xen-blkback-disable-barriers.patch

@@ -0,0 +1,11 @@
+--- linux-2.6.38.3/drivers/xen/blkback/xenbus.c	2011-08-18 00:08:53.000000000 +0200
++++ linux-2.6.38.3/drivers/xen/blkback/xenbus.c.new	2011-08-18 14:37:46.615344310 +0200
+@@ -441,7 +441,7 @@
+ 		return;
+ 	}
+ 
+-	err = blkback_barrier(xbt, be, 1);
++	err = blkback_barrier(xbt, be, 0);
+ 	if (err)
+ 		goto abort;
+ 

series-xenlinux.conf

@@ -847,3 +847,4 @@
 	patches.fixes/xen-blkfront-connect-overflow.patch
 	patches.fixes/xencons_close_deadlock.patch
 	patches.fixes/xen-disable-cdrom-dbgprints.diff
+	patches.xen/xen-blkback-disable-barriers.patch