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/configs/chromebook_link64_defconfig b/configs/chromebook_link64_defconfig
index 147cf68..c43d9dc 100644
--- a/configs/chromebook_link64_defconfig
+++ b/configs/chromebook_link64_defconfig
@@ -35,7 +35,7 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y
 CONFIG_SPL_DM_SPI_FLASH=y
-CONFIG_SPL_NET_SUPPORT=y
+CONFIG_SPL_NET=y
 CONFIG_SPL_PCI=y
 CONFIG_SPL_PCH=y
 CONFIG_SPL_RTC=y