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/mx28evk_auart_console_defconfig b/configs/mx28evk_auart_console_defconfig
index 953a5ae..9346efb 100644
--- a/configs/mx28evk_auart_console_defconfig
+++ b/configs/mx28evk_auart_console_defconfig
@@ -10,7 +10,7 @@
 CONFIG_IMX_CONFIG=""
 CONFIG_SPL_TEXT_BASE=0x00001000
 CONFIG_TARGET_MX28EVK=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_SPL=y
 CONFIG_SYS_LOAD_ADDR=0x42000000
 CONFIG_SYS_EXTRA_OPTIONS="MXS_AUART,MXS_AUART_BASE=MXS_UARTAPP3_BASE"