md: allow non-privileged uses to GET_*_INFO about raid arrays.

The info is already available in /proc/mdstat and /sys/block in
an accessible form so there is no point in putting a road-block in
the ioctl for information gathering.

Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/md.c

@@ -6054,8 +6054,15 @@ static int md_ioctl(struct block_device *bdev, fmode_t mode,
 	struct mddev *mddev = NULL;
 	int ro;
 
+	switch (cmd) {
+	case RAID_VERSION:
+	case GET_ARRAY_INFO:
+	case GET_DISK_INFO:
+		break;
+	default:
 		if (!capable(CAP_SYS_ADMIN))
 			return -EACCES;
+	}
 
 	/*
 	 * Commands dealing with the RAID driver but not any