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/lib/hang.c b/lib/hang.c
index 578ac78..2735774 100644
--- a/lib/hang.c
+++ b/lib/hang.c
@@ -24,7 +24,7 @@
 {
 #if !defined(CONFIG_SPL_BUILD) || \
 		(CONFIG_IS_ENABLED(LIBCOMMON_SUPPORT) && \
-		 CONFIG_IS_ENABLED(SERIAL_SUPPORT))
+		 CONFIG_IS_ENABLED(SERIAL))
 	puts("### ERROR ### Please RESET the board ###\n");
 #endif
 	bootstage_error(BOOTSTAGE_ID_NEED_RESET);