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/usb_mass_storage.c b/cmd/usb_mass_storage.c
index 0415591..03b7e21 100644
--- a/cmd/usb_mass_storage.c
+++ b/cmd/usb_mass_storage.c
@@ -19,7 +19,7 @@
 static int ums_read_sector(struct ums *ums_dev,
 			   ulong start, lbaint_t blkcnt, void *buf)
 {
-	block_dev_desc_t *block_dev = &ums_dev->block_dev;
+	struct blk_desc *block_dev = &ums_dev->block_dev;
 	lbaint_t blkstart = start + ums_dev->start_sector;
 
 	return block_dev->block_read(block_dev, blkstart, blkcnt, buf);
@@ -28,7 +28,7 @@
 static int ums_write_sector(struct ums *ums_dev,
 			    ulong start, lbaint_t blkcnt, const void *buf)
 {
-	block_dev_desc_t *block_dev = &ums_dev->block_dev;
+	struct blk_desc *block_dev = &ums_dev->block_dev;
 	lbaint_t blkstart = start + ums_dev->start_sector;
 
 	return block_dev->block_write(block_dev, blkstart, blkcnt, buf);
@@ -53,7 +53,7 @@
 static int ums_init(const char *devtype, const char *devnums)
 {
 	char *s, *t, *devnum, *name;
-	block_dev_desc_t *block_dev;
+	struct blk_desc *block_dev;
 	int ret;
 	struct ums *ums_new;