ofw: Cast function pointer to proper type

clang 15 insists that we call entry() via a function prototype. Rather
than copping out and using (...), cast it to the same prototype that's
used elsewhere (with tweaks to pointers to make them fit into that
prototype). No functional change.

Sponsored by:		Netflix

stand/libofw/openfirm.c

@@ -772,6 +772,7 @@ OF_chain(void *virt, u_int size, void (*entry)(), void *arg, u_int len)
 	if (size > 0)
 		OF_release(virt, size);
 #endif
-	entry(0, 0, openfirmware, arg, len);
+	((int (*)(u_long, u_long, u_long, void *, u_long))entry)
+	    (0, 0, (u_long)openfirmware, arg, len);
 }
 #endif