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/sama5d27_giantboard_defconfig b/configs/sama5d27_giantboard_defconfig
index 4a3fcfe..169b693 100644
--- a/configs/sama5d27_giantboard_defconfig
+++ b/configs/sama5d27_giantboard_defconfig
@@ -14,7 +14,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="at91-sama5d27_giantboard"
 CONFIG_SPL_TEXT_BASE=0x200000
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL_DRIVERS_MISC=y
 CONFIG_SPL=y
 CONFIG_DEBUG_UART_BOARD_INIT=y