serial: Rename SERIAL_SUPPORT to SERIAL

Rename these options so that CONFIG_IS_ENABLED can be used with them.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/cl-som-imx7_defconfig b/configs/cl-som-imx7_defconfig
index 2500916..a8faf0e 100644
--- a/configs/cl-som-imx7_defconfig
+++ b/configs/cl-som-imx7_defconfig
@@ -13,7 +13,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx7d-sdb"
 CONFIG_TARGET_CL_SOM_IMX7=y
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_SPL_SPI_FLASH_SUPPORT=y
 CONFIG_SPL_SPI_SUPPORT=y