dm: Drop the block_dev_desc_t typedef

Use 'struct' instead of a typdef. Also since 'struct block_dev_desc' is long
and causes 80-column violations, rename it to struct blk_desc.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
diff --git a/cmd/zfs.c b/cmd/zfs.c
index 0aed29e..9076a8a 100644
--- a/cmd/zfs.c
+++ b/cmd/zfs.c
@@ -39,7 +39,7 @@
 	int part;
 	ulong addr = 0;
 	disk_partition_t info;
-	block_dev_desc_t *dev_desc;
+	struct blk_desc *dev_desc;
 	char buf[12];
 	unsigned long count;
 	const char *addr_str;
@@ -135,7 +135,7 @@
 {
 	const char *filename = "/";
 	int part;
-	block_dev_desc_t *dev_desc;
+	struct blk_desc *dev_desc;
 	disk_partition_t info;
 	struct device_s vdev;