net: Rename SPL_NET_SUPPORT to SPL_NET

Rename this option so that CONFIG_IS_ENABLED can be used with it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/Makefile b/common/Makefile
index fb0256b..f785260 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -69,7 +69,7 @@
 obj-$(CONFIG_SPL_HASH_SUPPORT) += hash.o
 obj-$(CONFIG_TPL_HASH_SUPPORT) += hash.o
 obj-$(CONFIG_SPL_LOAD_FIT) += common_fit.o
-obj-$(CONFIG_SPL_NET_SUPPORT) += miiphyutil.o
+obj-$(CONFIG_SPL_NET) += miiphyutil.o
 obj-$(CONFIG_$(SPL_TPL_)OF_LIBFDT) += fdt_support.o
 
 ifdef CONFIG_SPL_USB_HOST