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/include/configs/am43xx_evm.h b/include/configs/am43xx_evm.h
index a0d2b36..663f861 100644
--- a/include/configs/am43xx_evm.h
+++ b/include/configs/am43xx_evm.h
@@ -80,7 +80,7 @@
 #define CONFIG_AM437X_USB2PHY2_HOST
 #endif
 
-#if defined(CONFIG_SPL_BUILD) && !defined(CONFIG_SPL_USBETH_SUPPORT)
+#if defined(CONFIG_SPL_BUILD) && !defined(CONFIG_SPL_USB_ETHER)
 #undef CONFIG_USB_DWC3_PHY_OMAP
 #undef CONFIG_USB_DWC3_OMAP
 #undef CONFIG_USB_DWC3