spl: Kconfig: Rename SPL_USBETH_SUPPORT to SPL_USB_ETHER to match with the U-boot CONFIG

Rename CONFIG_SPL_USBETH_SUPPORT to CONFIG_SPL_USB_ETHER.

This enables users to block text using CONFIG_IS_ENABLED() instead
of resorting to #if ladders with SPL and non-SPL cases.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index f58163c..9609fce 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -680,7 +680,7 @@
 
 if SPL_USB_GADGET_SUPPORT
 
-config SPL_USBETH_SUPPORT
+config SPL_USB_ETHER
 	bool "Support USB Ethernet drivers"
 	help
 	  Enable access to the USB network subsystem and associated