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/T1042D4RDB_SDCARD_defconfig b/configs/T1042D4RDB_SDCARD_defconfig
index 4f10380..4efa307 100644
--- a/configs/T1042D4RDB_SDCARD_defconfig
+++ b/configs/T1042D4RDB_SDCARD_defconfig
@@ -7,7 +7,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="t1042d4rdb"
 CONFIG_SPL_TEXT_BASE=0xFFFD8000
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL=y
 CONFIG_MPC85xx=y