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/etamin_defconfig b/configs/etamin_defconfig
index 00cb35d..77901a8 100644
--- a/configs/etamin_defconfig
+++ b/configs/etamin_defconfig
@@ -15,7 +15,7 @@
 CONFIG_SYS_MPUCLK=300
 CONFIG_TARGET_ETAMIN=y
 CONFIG_SPL_MMC=y
-CONFIG_SPL_SERIAL_SUPPORT=y
+CONFIG_SPL_SERIAL=y
 CONFIG_BOOTCOUNT_BOOTLIMIT=3
 CONFIG_SPL=y
 CONFIG_ENV_OFFSET_REDUND=0xB80000