drm/msm: 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/20211217003752.3946210-30-javierm@redhat.com

drivers/gpu/drm/msm/msm_drv.c

@@ -518,6 +518,9 @@ static int msm_drm_init(struct device *dev, const struct drm_driver *drv)
 	struct msm_mdss *mdss;
 	int ret, i;
 
+	if (drm_firmware_drivers_only())
+		return -ENODEV;
+
 	ddev = drm_dev_alloc(drv, dev);
 	if (IS_ERR(ddev)) {
 		DRM_DEV_ERROR(dev, "failed to allocate drm_device\n");