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/brppt2_defconfig b/configs/brppt2_defconfig
index bcd46c1..af15a58 100644
--- a/configs/brppt2_defconfig
+++ b/configs/brppt2_defconfig
@@ -16,7 +16,7 @@
 CONFIG_TARGET_BRPPT2=y
 CONFIG_SYS_MALLOC_LEN=0xa00000
 CONFIG_DEFAULT_DEVICE_TREE="imx6dl-brppt2"
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SYS_BOOTCOUNT_ADDR=0x020CC068
 CONFIG_SPL=y
 CONFIG_SYS_BOOTCOUNT_SINGLEWORD=y