drm/mcde: Add support for the nomodeset kernel parameter

According to disable Documentation/admin-guide/kernel-parameters.txt, this
parameter can be used to disable kernel modesetting.

DRM drivers will not perform display-mode changes or accelerated rendering
and only the system framebuffer will be available if it was set-up.

But only a few DRM drivers currently check for nomodeset, make this driver
to also support the command line parameter.
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211217003752.3946210-28-javierm@redhat.com

drivers/gpu/drm/mcde/mcde_drv.c

@@ -491,6 +491,9 @@ static int __init mcde_drm_register(void)
 {
 	int ret;
 
+	if (drm_firmware_drivers_only())
+		return -ENODEV;
+
 	ret = platform_register_drivers(component_drivers,
 					ARRAY_SIZE(component_drivers));
 	if (ret)