generalize gpio

src/gpio.rs

@@ -488,6 +488,7 @@ macro_rules! gpio {
     }
 }
 
+// TODO, check if some GPIO should be excluded
 gpio!(GPIOA, gpioa, gpioa, gpioaen, gpioarst, PAx, [
     PA0: (pa0, 0, Input<Floating>, AFRL),
     PA1: (pa1, 1, Input<Floating>, AFRL),