drm/vram-helper: Remove invariant parameters from internal kmap function

The parameters map and is_iomem are always of the same value. Removed them
to prepares the function for conversion to struct dma_buf_map.

v4:
	* don't check for !kmap->virtual; will always be false
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Christian König <christian.koenig@amd.com>
Tested-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201103093015.1063-2-tzimmermann@suse.de

drivers/gpu/drm/drm_gem_vram_helper.c

@@ -378,32 +378,22 @@ int drm_gem_vram_unpin(struct drm_gem_vram_object *gbo)
 }
 EXPORT_SYMBOL(drm_gem_vram_unpin);
 
-static void *drm_gem_vram_kmap_locked(struct drm_gem_vram_object *gbo,
-				      bool map, bool *is_iomem)
+static void *drm_gem_vram_kmap_locked(struct drm_gem_vram_object *gbo)
 {
 	int ret;
 	struct ttm_bo_kmap_obj *kmap = &gbo->kmap;
+	bool is_iomem;
 
 	if (gbo->kmap_use_count > 0)
 		goto out;
 
-	if (kmap->virtual || !map)
-		goto out;
-
 	ret = ttm_bo_kmap(&gbo->bo, 0, gbo->bo.num_pages, kmap);
 	if (ret)
 		return ERR_PTR(ret);
 
 out:
-	if (!kmap->virtual) {
-		if (is_iomem)
-			*is_iomem = false;
-		return NULL; /* not mapped; don't increment ref */
-	}
 	++gbo->kmap_use_count;
-	if (is_iomem)
-		return ttm_kmap_obj_virtual(kmap, is_iomem);
-	return kmap->virtual;
+	return ttm_kmap_obj_virtual(kmap, &is_iomem);
 }
 
 static void drm_gem_vram_kunmap_locked(struct drm_gem_vram_object *gbo)
@@ -448,7 +438,7 @@ void *drm_gem_vram_vmap(struct drm_gem_vram_object *gbo)
 	ret = drm_gem_vram_pin_locked(gbo, 0);
 	if (ret)
 		goto err_ttm_bo_unreserve;
-	base = drm_gem_vram_kmap_locked(gbo, true, NULL);
+	base = drm_gem_vram_kmap_locked(gbo);
 	if (IS_ERR(base)) {
 		ret = PTR_ERR(base);
 		goto err_drm_gem_vram_unpin_locked;