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/imx8mq_phanbell_defconfig b/configs/imx8mq_phanbell_defconfig
index 427beb9..e5d5d9e 100644
--- a/configs/imx8mq_phanbell_defconfig
+++ b/configs/imx8mq_phanbell_defconfig
@@ -12,7 +12,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx8mq-phanbell"
 CONFIG_SPL_TEXT_BASE=0x7E1000
 CONFIG_TARGET_IMX8MQ_PHANBELL=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_SYS_LOAD_ADDR=0x40480000
 CONFIG_FIT=y