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/lib/gunzip.c b/lib/gunzip.c
index da0c76c..6d65ccc 100644
--- a/lib/gunzip.c
+++ b/lib/gunzip.c
@@ -105,7 +105,7 @@
 }
 
 int gzwrite(unsigned char *src, int len,
-	    struct block_dev_desc *dev,
+	    struct blk_desc *dev,
 	    unsigned long szwritebuf,
 	    u64 startoffs,
 	    u64 szexpected)