nbd: move multi-connection bit to unused value

Bit #7 is already used, move to bit #8 which is the first unused
one.

Fixes: 9561a7ade0c2 ("nbd: add multi-connection support")
Signed-off-by: Jens Axboe <axboe@fb.com>

include/uapi/linux/nbd.h

@@ -43,7 +43,7 @@ enum {
 #define NBD_FLAG_SEND_FLUSH	(1 << 2) /* can flush writeback cache */
 /* there is a gap here to match userspace */
 #define NBD_FLAG_SEND_TRIM	(1 << 5) /* send trim/discard */
-#define NBD_FLAG_CAN_MULTI_CONN	(1 << 7)	/* Server supports multiple connections per export. */
+#define NBD_FLAG_CAN_MULTI_CONN	(1 << 8)	/* Server supports multiple connections per export. */
 
 /* userspace doesn't need the nbd_device structure */