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/mt7629_rfb_defconfig b/configs/mt7629_rfb_defconfig
index ea1a4ba..cd993bc 100644
--- a/configs/mt7629_rfb_defconfig
+++ b/configs/mt7629_rfb_defconfig
@@ -9,7 +9,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="mt7629-rfb"
 CONFIG_SPL_TEXT_BASE=0x201000
 CONFIG_TARGET_MT7629=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL_STACK_R_ADDR=0x40800000
 CONFIG_SPL_PAYLOAD="u-boot-lzma.img"