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/board/tcl/sl50/board.c b/board/tcl/sl50/board.c
index f79bb9d..933a407 100644
--- a/board/tcl/sl50/board.c
+++ b/board/tcl/sl50/board.c
@@ -299,7 +299,7 @@
  * Build in only these cases to avoid warnings about unused variables
  * when we build an SPL that has neither option but full U-Boot will.
  */
-#if ((defined(CONFIG_SPL_ETH_SUPPORT) || defined(CONFIG_SPL_USBETH_SUPPORT)) \
+#if ((defined(CONFIG_SPL_ETH_SUPPORT) || defined(CONFIG_SPL_USB_ETHER)) \
 		&& defined(CONFIG_SPL_BUILD)) || \
 	((defined(CONFIG_DRIVER_TI_CPSW) || \
 	  defined(CONFIG_USB_ETHER) && defined(CONFIG_MUSB_GADGET)) && \
@@ -371,7 +371,7 @@
 
 #endif
 #if defined(CONFIG_USB_ETHER) && \
-	(!defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_USBETH_SUPPORT))
+	(!defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_USB_ETHER))
 	if (is_valid_ether_addr(mac_addr))
 		eth_env_set_enetaddr("usbnet_devaddr", mac_addr);