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/brppt1_nand_defconfig b/configs/brppt1_nand_defconfig
index 59aa2cc..88f281c 100644
--- a/configs/brppt1_nand_defconfig
+++ b/configs/brppt1_nand_defconfig
@@ -12,7 +12,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="am335x-brppt1-nand"
 CONFIG_AM33XX=y
 CONFIG_TARGET_BRPPT1=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 # CONFIG_EXPERT is not set
 CONFIG_SYS_LOAD_ADDR=0x80000000