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/uniphier_ld4_sld8_defconfig b/configs/uniphier_ld4_sld8_defconfig
index 02e1325..1c2533c 100644
--- a/configs/uniphier_ld4_sld8_defconfig
+++ b/configs/uniphier_ld4_sld8_defconfig
@@ -7,7 +7,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="uniphier-ld4-ref"
 CONFIG_SPL_TEXT_BASE=0x00040000
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_MICRO_SUPPORT_CARD=y
 CONFIG_SYS_LOAD_ADDR=0x85000000