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/mx23_olinuxino_defconfig b/configs/mx23_olinuxino_defconfig
index 8bdc087..7fc7cc6 100644
--- a/configs/mx23_olinuxino_defconfig
+++ b/configs/mx23_olinuxino_defconfig
@@ -11,7 +11,7 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx23-olinuxino"
 CONFIG_SPL_TEXT_BASE=0x00001000
 CONFIG_TARGET_MX23_OLINUXINO=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 # CONFIG_SYS_MALLOC_F is not set
 CONFIG_SYS_LOAD_ADDR=0x42000000