greenhills: fix enumerated type mixed using build warning

CC:  irq/irq_initialize.c "ioexpander/gpio.c", line 386: warning #188-D: enumerated type mixed with
          another type
            *ptr = dev->gp_pintype;
                 ^

Signed-off-by: guoshichao <[email protected]>

drivers/ioexpander/gpio.c

@@ -330,7 +330,7 @@ static int gpio_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
             (FAR enum gpio_pintype_e *)((uintptr_t)arg);
           DEBUGASSERT(ptr != NULL);
 
-          *ptr = dev->gp_pintype;
+          *ptr = (FAR enum gpio_pintype_e)dev->gp_pintype;
           ret = OK;
         }
         break;