drm: Convert drm_legacy_ctxbitmap_init to void return type

It can't fail really.

Also remove the redundant kms check Peter added.

Cc: Peter Antoine <peter.antoine@intel.com>
Reviewed-by: Peter Antoine <peter.antoine@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
diff --git a/drivers/gpu/drm/drm_context.c b/drivers/gpu/drm/drm_context.c
index 32958da..192a5f9 100644
--- a/drivers/gpu/drm/drm_context.c
+++ b/drivers/gpu/drm/drm_context.c
@@ -89,14 +89,13 @@
  *
  * Initialise the drm_device::ctx_idr
  */
-int drm_legacy_ctxbitmap_init(struct drm_device * dev)
+void drm_legacy_ctxbitmap_init(struct drm_device * dev)
 {
 	if (!drm_core_check_feature(dev, DRIVER_KMS_LEGACY_CONTEXT) &&
 	    drm_core_check_feature(dev, DRIVER_MODESET))
-		return -EINVAL;
+		return;
 
 	idr_init(&dev->ctx_idr);
-	return 0;
 }
 
 /**