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/ls1021aiot_sdcard_defconfig b/configs/ls1021aiot_sdcard_defconfig
index c2fc09c..dc631ee 100644
--- a/configs/ls1021aiot_sdcard_defconfig
+++ b/configs/ls1021aiot_sdcard_defconfig
@@ -11,7 +11,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="ls1021a-iot-duart"
 CONFIG_SPL_TEXT_BASE=0x10000000
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_AHCI=y
 CONFIG_SYS_LOAD_ADDR=0x82000000