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/am43xx_evm_defconfig b/configs/am43xx_evm_defconfig
index f5f2e19..4960ec2 100644
--- a/configs/am43xx_evm_defconfig
+++ b/configs/am43xx_evm_defconfig
@@ -21,7 +21,7 @@
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_ECC=y
 CONFIG_SPL_NAND_BASE=y
-CONFIG_SPL_NET_SUPPORT=y
+CONFIG_SPL_NET=y
 CONFIG_SPL_NET_VCI_STRING="AM43xx U-Boot SPL"
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_USB_HOST=y