s390/virtio: change virtio_feature_desc:features type to __le32

The feature member of virtio_feature_desc contains little endian
values, given that it contents will be converted with
le32_to_cpu(). The "wrong" __u32 type leads to the sparse warnings
below.
In order to avoid them, use the correct __le32 type instead.

drivers/s390/virtio/virtio_ccw.c:749:14: warning: cast to restricted __le32
drivers/s390/virtio/virtio_ccw.c:762:28: warning: cast to restricted __le32
Acked-by: NHalil Pasic <pasic@linux.vnet.ibm.com>
Acked-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/virtio/virtio_ccw.c

@@ -87,7 +87,7 @@ struct vq_info_block {
 } __packed;
 
 struct virtio_feature_desc {
-	__u32 features;
+	__le32 features;
 	__u8 index;
 } __packed;