xen/scsifront: remove unused GRANT_INVALID_REF definition

GRANT_INVALID_REF isn't used in scsifront, so remove it.
Signed-off-by: NJuergen Gross <jgross@suse.com>
Reviewed-by: NBoris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NJuergen Gross <jgross@suse.com>

drivers/scsi/xen-scsifront.c

@@ -58,9 +58,6 @@
 
 #include <asm/xen/hypervisor.h>
 
-
-#define GRANT_INVALID_REF	0
-
 #define VSCSIFRONT_OP_ADD_LUN	1
 #define VSCSIFRONT_OP_DEL_LUN	2
 #define VSCSIFRONT_OP_READD_LUN	3