Fixed GPIO read operation

Author: toyowata

libraries/mbed/targets/hal/TARGET_NXP/TARGET_LPC11XX/gpio_api.c

@@ -37,7 +37,7 @@ void gpio_init(gpio_t *obj, PinName pin, PinDirection direction) {
     obj->pin = pin;
     LPC_GPIO_TypeDef *port_reg = ((LPC_GPIO_TypeDef *) (LPC_GPIO0_BASE + (((pin & 0xF000) >> PORT_SHIFT) * 0x10000)));
 
-    obj->reg_mask_read = &port_reg->MASKED_ACCESS[gpio_set(pin) + 1];
+    obj->reg_mask_read = &port_reg->MASKED_ACCESS[1 << gpio_set(pin)];
     obj->reg_dir       = &port_reg->DIR;
     obj->reg_write     = &port_reg->DATA;