lint: add (void) parameter to pass -Wstrict-prototypes

Note there was one place where a non-strict prototype was actually being used
with an argument, in `zmk_hog_init`. In this case, the actual argument type was
added instead.

app/src/endpoints.c

@@ -322,7 +322,7 @@ static int zmk_endpoints_init(const struct device *_arg) {
     return 0;
 }
 
-static void disconnect_current_endpoint() {
+static void disconnect_current_endpoint(void) {
     zmk_hid_keyboard_clear();
     zmk_hid_consumer_clear();
 #if IS_ENABLED(CONFIG_ZMK_MOUSE)