gpio: configure STATUS input gpio

RI won't be accessible due to it being used by the kernel as an 
interrupt source, so we can check the STATUS pin (CE only) which will 
allow us to know precisely when the modem is shut down.

src/manager.h

@@ -46,6 +46,7 @@ struct EG25Manager {
 
     struct gpiod_chip *gpiochip[2];
     struct gpiod_line *gpio_out[5];
+    struct gpiod_line *gpio_in[2];
 };
 
 void modem_configure(struct EG25Manager *data);