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/arch/arm/mach-stm32mp/Kconfig b/arch/arm/mach-stm32mp/Kconfig
index 4a57014..cd0e879 100644
--- a/arch/arm/mach-stm32mp/Kconfig
+++ b/arch/arm/mach-stm32mp/Kconfig
@@ -15,7 +15,7 @@
 	select SPL_PINCTRL
 	select SPL_REGMAP
 	select SPL_DM_RESET
-	select SPL_SERIAL_SUPPORT
+	select SPL_SERIAL
 	select SPL_SYSCON
 	select SPL_WATCHDOG if WATCHDOG
 	imply BOOTSTAGE_STASH if SPL_BOOTSTAGE