Kconfig: rename CONFIG_SPL_USB_GADGET_SUPPORT as CONFIG_SPL_USB_GADGET

The SPL option for USB gadget should be named after the option for u-boot
(CONFIG_USB_GADGET)

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
diff --git a/arch/arm/mach-imx/mx6/Kconfig b/arch/arm/mach-imx/mx6/Kconfig
index e7cce46..3d56346 100644
--- a/arch/arm/mach-imx/mx6/Kconfig
+++ b/arch/arm/mach-imx/mx6/Kconfig
@@ -263,7 +263,7 @@
 	select SPL_PINCTRL if SPL
 	select SPL_SEPARATE_BSS if SPL
 	select SPL_SERIAL_SUPPORT if SPL
-	select SPL_USB_GADGET_SUPPORT if SPL
+	select SPL_USB_GADGET if SPL
 	select SPL_USB_HOST_SUPPORT if SPL
 	select SPL_USB_SDP_SUPPORT if SPL
 	select SPL_WATCHDOG_SUPPORT if SPL