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/configs/apalis_imx6_defconfig b/configs/apalis_imx6_defconfig
index 133fc1a..e02d9bc 100644
--- a/configs/apalis_imx6_defconfig
+++ b/configs/apalis_imx6_defconfig
@@ -23,7 +23,7 @@
 CONFIG_SPL_DMA_SUPPORT=y
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_USB_HOST_SUPPORT=y
-CONFIG_SPL_USB_GADGET_SUPPORT=y
+CONFIG_SPL_USB_GADGET=y
 CONFIG_SPL_USB_SDP_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Apalis iMX6 # "