dm: doc: Correct of-platdata driver name

Add a note about the driver name in the of-platdata documentation since
the naming must follow the compatible string.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/driver-model/of-plat.rst b/doc/driver-model/of-plat.rst
index a38e58e..557957d 100644
--- a/doc/driver-model/of-plat.rst
+++ b/doc/driver-model/of-plat.rst
@@ -269,7 +269,7 @@
     };
 
     U_BOOT_DRIVER(mmc_drv) = {
-            .name           = "mmc",
+            .name           = "vendor_mmc",  /* matches compatible string */
             .id             = UCLASS_MMC,
             .of_match       = mmc_ids,
             .ofdata_to_platdata = mmc_ofdata_to_platdata,