mfd: vexpress: Make the driver optional for arm and arm64

The driver can be used on either arm or arm64 platforms, but
the latter doesn't have any platform-specific configuration
options, so it must be possible to manually enable the driver.

As the gpiolib is optional for arm64 arch, the gpio/led code
must be compiled conditionally.
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/Kconfig

@@ -1151,7 +1151,8 @@ config MCP_UCB1200_TS
 endmenu
 
 config VEXPRESS_CONFIG
-	bool
+	bool "ARM Versatile Express platform infrastructure"
+	depends on ARM || ARM64
 	help
 	  Platform configuration infrastructure for the ARM Ltd.
 	  Versatile Express.

drivers/mfd/vexpress-sysreg.c

@@ -351,6 +351,8 @@ void __init vexpress_sysreg_of_early_init(void)
 }
 
 
+#ifdef CONFIG_GPIOLIB
+
 #define VEXPRESS_SYSREG_GPIO(_name, _reg, _value) \
 	[VEXPRESS_GPIO_##_name] = { \
 		.reg = _reg, \
@@ -445,6 +447,8 @@ struct gpio_led_platform_data vexpress_sysreg_leds_pdata = {
 	.leds = vexpress_sysreg_leds,
 };
 
+#endif
+
 
 static ssize_t vexpress_sysreg_sys_id_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
@@ -480,6 +484,9 @@ static int vexpress_sysreg_probe(struct platform_device *pdev)
 	setup_timer(&vexpress_sysreg_config_timer,
 			vexpress_sysreg_config_complete, 0);
 
+	vexpress_sysreg_dev = &pdev->dev;
+
+#ifdef CONFIG_GPIOLIB
 	vexpress_sysreg_gpio_chip.dev = &pdev->dev;
 	err = gpiochip_add(&vexpress_sysreg_gpio_chip);
 	if (err) {
@@ -490,11 +497,10 @@ static int vexpress_sysreg_probe(struct platform_device *pdev)
 		return err;
 	}
 
-	vexpress_sysreg_dev = &pdev->dev;
-
 	platform_device_register_data(vexpress_sysreg_dev, "leds-gpio",
 			PLATFORM_DEVID_AUTO, &vexpress_sysreg_leds_pdata,
 			sizeof(vexpress_sysreg_leds_pdata));
+#endif
 
 	device_create_file(vexpress_sysreg_dev, &dev_attr_sys_id);