fix void param declarations & prototypes

These should be funcname(void) rather than funcname(). Found by
searching for "() {" in C files.

Bug: aomedia:3416
Change-Id: I119133dc0fe78cfb24f072da70ca4ceea8e19431
diff --git a/tools/auto_refactor/c_files/struct_code.c b/tools/auto_refactor/c_files/struct_code.c
index e14372c..7f24d41 100644
--- a/tools/auto_refactor/c_files/struct_code.c
+++ b/tools/auto_refactor/c_files/struct_code.c
@@ -46,4 +46,4 @@
   } z;
 } T7;
 
-int main() {}
+int main(void) {}