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/include/configs/mt7628.h b/include/configs/mt7628.h
index 9e35b40..e53e6a0 100644
--- a/include/configs/mt7628.h
+++ b/include/configs/mt7628.h
@@ -25,7 +25,7 @@
 #define CONFIG_SYS_CBSIZE		1024
 
 /* Serial SPL */
-#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_SERIAL_SUPPORT)
+#if defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_SERIAL)
 #define CONFIG_SYS_NS16550_MEM32
 #define CONFIG_SYS_NS16550_CLK		40000000
 #define CONFIG_SYS_NS16550_REG_SIZE	-4