configs: Migrate CONFIG_USB_STORAGE

In some cases we were missing CONFIG_USB=y so enable that when needed.

Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/digsy_mtc_RAMBOOT_defconfig b/configs/digsy_mtc_RAMBOOT_defconfig
index 0e708cd..d0743c8 100644
--- a/configs/digsy_mtc_RAMBOOT_defconfig
+++ b/configs/digsy_mtc_RAMBOOT_defconfig
@@ -20,4 +20,6 @@
 CONFIG_CMD_CACHE=y
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_FAT=y
+CONFIG_USB=y
+CONFIG_USB_STORAGE=y
 CONFIG_OF_LIBFDT=y