Enable USB2 driver.

Change-Id: I3384c36721bc5d9cf1079a6a58f838316f175381
diff --git a/arch/arm/configs/gfsc100_defconfig b/arch/arm/configs/gfsc100_defconfig
index 298bab9..da48860 100644
--- a/arch/arm/configs/gfsc100_defconfig
+++ b/arch/arm/configs/gfsc100_defconfig
@@ -238,6 +238,7 @@
 CONFIG_USB_SERIAL_CONSOLE=y
 CONFIG_USB_SERIAL_GENERIC=y
 CONFIG_USB_SERIAL_PL2303=y
+CONFIG_DWC_OTG=y
 CONFIG_RTC_CLASS=y
 # CONFIG_RTC_HCTOSYS is not set
 # CONFIG_RTC_INTF_SYSFS is not set