coreboot: Minor - avoid K&R style function declaration

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/src/fw/coreboot.c b/src/fw/coreboot.c
index a47f524..3b9df14 100644
--- a/src/fw/coreboot.c
+++ b/src/fw/coreboot.c
@@ -506,7 +506,7 @@
             break;
         case PAYLOAD_SEGMENT_ENTRY: {
             dprintf(1, "Calling addr %p\n", dest);
-            void (*func)() = dest;
+            void (*func)(void) = dest;
             func();
             return;
         }