extmod/network_wiznet5k: Correct interrupt pin enable for W5100S.

Signed-off-by: Matt Lloyd <dps.lwk@gmail.com>

extmod/network_wiznet5k.c

@@ -225,7 +225,7 @@ STATIC void wiznet5k_init(void) {
         setSn_IMR(0, Sn_IR_RECV);
         #if _WIZCHIP_ == W5100S
         // Enable interrupt pin
-        setMR(MR2_G_IEN);
+        setMR2(MR2_G_IEN);
         #endif
 
         mp_hal_pin_input(wiznet5k_obj.pin_intn);