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/fs/ext4/ext4fs.c b/fs/ext4/ext4fs.c
index 258b937..43c8897 100644
--- a/fs/ext4/ext4fs.c
+++ b/fs/ext4/ext4fs.c
@@ -198,7 +198,7 @@
 	return ext4fs_read_file(ext4fs_file, 0, len, buf, actread);
 }
 
-int ext4fs_probe(block_dev_desc_t *fs_dev_desc,
+int ext4fs_probe(struct blk_desc *fs_dev_desc,
 		 disk_partition_t *fs_partition)
 {
 	ext4fs_set_blk_dev(fs_dev_desc, fs_partition);