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/stdio.h b/include/stdio.h
index 039f7df..1939a48 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -10,9 +10,9 @@
 
 /* stdout */
 #if !defined(CONFIG_SPL_BUILD) || \
-	(defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_SERIAL_SUPPORT)) || \
+	(defined(CONFIG_TPL_BUILD) && defined(CONFIG_TPL_SERIAL)) || \
 	(defined(CONFIG_SPL_BUILD) && !defined(CONFIG_TPL_BUILD) && \
-		defined(CONFIG_SPL_SERIAL_SUPPORT))
+		defined(CONFIG_SPL_SERIAL))
 void putc(const char c);
 void puts(const char *s);
 int __printf(1, 2) printf(const char *fmt, ...);