drm/ingenic: 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>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20211217003752.3946210-27-javierm@redhat.com

drivers/gpu/drm/ingenic/ingenic-drm-drv.c

@@ -1543,6 +1543,9 @@ static int ingenic_drm_init(void)
 {
 	int err;
 
+	if (drm_firmware_drivers_only())
+		return -ENODEV;
+
 	if (IS_ENABLED(CONFIG_DRM_INGENIC_IPU)) {
 		err = platform_driver_register(ingenic_ipu_driver_ptr);
 		if (err)