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/spl_net.c b/common/spl/spl_net.c
index 8883109..ef13145 100644
--- a/common/spl/spl_net.c
+++ b/common/spl/spl_net.c
@@ -15,7 +15,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#if defined(CONFIG_SPL_ETH_SUPPORT) || defined(CONFIG_SPL_USBETH_SUPPORT)
+#if defined(CONFIG_SPL_ETH_SUPPORT) || defined(CONFIG_SPL_USB_ETHER)
 static ulong spl_net_load_read(struct spl_load_info *load, ulong sector,
 			       ulong count, void *buf)
 {
@@ -83,7 +83,7 @@
 		      spl_net_load_image_cpgmac);
 #endif
 
-#ifdef CONFIG_SPL_USBETH_SUPPORT
+#ifdef CONFIG_SPL_USB_ETHER
 int spl_net_load_image_usb(struct spl_image_info *spl_image,
 			   struct spl_boot_device *bootdev)
 {