util/msrtool: Don't use old style function definition

Use "int foo(void)" instead of old-style "int foo()".

Change-Id: Ieb151c2db1c0ee9222dbacccae78ca725bdcde08
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77498
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/msrtool/msrtool.c

@@ -87,7 +87,7 @@ static void *add_target(const struct targetdef *t) {
 	return targets;
 }
 
-static int found_system() {
+static int found_system(void) {
 	if (!sys || (sys && !sys->name)) {
 		fprintf(stderr, "Unable to detect the current operating system!\n");
 		fprintf(stderr, "On Linux, please run 'modprobe msr' and try again.\n");