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/mx6sabresd_defconfig b/configs/mx6sabresd_defconfig
index e0202ef..1857c18 100644
--- a/configs/mx6sabresd_defconfig
+++ b/configs/mx6sabresd_defconfig
@@ -19,7 +19,7 @@
 CONFIG_SPL_I2C_SUPPORT=y
 CONFIG_SPL_OS_BOOT=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_SPL_WATCHDOG_SUPPORT=y
 CONFIG_HUSH_PARSER=y