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/clearfog_defconfig b/configs/clearfog_defconfig
index 090abcd..f613107 100644
--- a/configs/clearfog_defconfig
+++ b/configs/clearfog_defconfig
@@ -13,7 +13,7 @@
 CONFIG_DM_GPIO=y
 CONFIG_DEFAULT_DEVICE_TREE="armada-388-clearfog"
 CONFIG_SPL_TEXT_BASE=0x40000030
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_DEBUG_UART_BASE=0xd0012000
 CONFIG_DEBUG_UART_CLOCK=250000000