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/board/mpl/pip405/README b/board/mpl/pip405/README
index 1b73dbe..e900c56 100644
--- a/board/mpl/pip405/README
+++ b/board/mpl/pip405/README
@@ -217,8 +217,8 @@
 Block device changes:
 ---------------------
 To allow the use of dos_part.c, mac_part.c and iso_part.c, the parameter
-block_dev_desc will be used when accessing the functions in these files. The block
-device descriptor (block_dev_desc) contains a pointer to the read routine of the
+blk_desc will be used when accessing the functions in these files. The block
+device descriptor (blk_desc) contains a pointer to the read routine of the
 device, which will be used to read blocks from the device.
 Renamed function ide_print to dev_print and moved it to the file disk/part.c to use
 it for IDE ATAPI and SCSI devices.