video: fbdev: gbefb: Only instantiate device when built for IP32

The gbefb driver not only registers a driver but also the device for that
driver. This is all well and good when run on the IP32 machines that are
supported by the driver but since the driver supports building with
COMPILE_TEST we might also be building on other platforms which do not have
this hardware and will crash instantiating the driver. Add an IS_ENABLED()
check so we compile out the device registration if we don't have the Kconfig
option for the machine enabled.

Fixes: 552ccf6b259d290c0c ("video: fbdev: gbefb: add COMPILE_TEST support")
Signed-off-by: Mark Brown <[e-mail]>
Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Maarten Lankhorst <[e-mail]>

drivers/video/fbdev/gbefb.c

···
 static int __init gbefb_init(void)
 {
 	int ret = platform_driver_register(&gbefb_driver);
-	if (!ret) {
+	if (IS_ENABLED(CONFIG_SGI_IP32) && !ret) {
 		gbefb_device = platform_device_alloc("gbefb", 0);
 		if (gbefb_device) {
 			ret = platform_device_add(gbefb_device);