dm: block: Rename device number member dev to devnum

This is a device number, and we want to use 'dev' to mean a driver model
device. Rename the member.

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 59bb4ee..14eed98 100644
--- a/cmd/usb_mass_storage.c
+++ b/cmd/usb_mass_storage.c
@@ -100,7 +100,7 @@
 		ums[ums_count].block_dev = *block_dev;
 
 		printf("UMS: LUN %d, dev %d, hwpart %d, sector %#x, count %#x\n",
-		       ums_count, ums[ums_count].block_dev.dev,
+		       ums_count, ums[ums_count].block_dev.devnum,
 		       ums[ums_count].block_dev.hwpart,
 		       ums[ums_count].start_sector,
 		       ums[ums_count].num_sectors);