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/verdin-imx8mm_defconfig b/configs/verdin-imx8mm_defconfig
index 193ec68..42b6803 100644
--- a/configs/verdin-imx8mm_defconfig
+++ b/configs/verdin-imx8mm_defconfig
@@ -18,7 +18,7 @@
 CONFIG_SPL_TEXT_BASE=0x7E1000
 CONFIG_TARGET_VERDIN_IMX8MM=y
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL=y
 CONFIG_DISTRO_DEFAULTS=y