kbuild: add static to prototypes

Warnings found via gcc -Wmissing-prototypes.

Signed-off-by: Trevor Keith <tsrk@tsrk.net>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
index a04da34..b55e72f 100644
--- a/scripts/kconfig/confdata.c
+++ b/scripts/kconfig/confdata.c
@@ -560,7 +560,7 @@
 	return 0;
 }
 
-int conf_split_config(void)
+static int conf_split_config(void)
 {
 	const char *name;
 	char path[128];