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/brxre1_defconfig b/configs/brxre1_defconfig
index 2f3f48e..346a10c 100644
--- a/configs/brxre1_defconfig
+++ b/configs/brxre1_defconfig
@@ -13,7 +13,7 @@
 CONFIG_SYS_MPUCLK=1000
 CONFIG_TARGET_BRXRE1=y
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_SYS_MALLOC_F_LEN=0x4000
 CONFIG_SPL=y
 CONFIG_ENV_OFFSET_REDUND=0x50000