drm/radeon: add radeon_bo_ref function

To be consistent with radeon_bo_unref, needed in the following patch.
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_object.c

@@ -236,6 +236,15 @@ void radeon_bo_kunmap(struct radeon_bo *bo)
 	ttm_bo_kunmap(&bo->kmap);
 }
 
+struct radeon_bo *radeon_bo_ref(struct radeon_bo *bo)
+{
+	if (bo == NULL)
+		return NULL;
+
+	ttm_bo_reference(&bo->tbo);
+	return bo;
+}
+
 void radeon_bo_unref(struct radeon_bo **bo)
 {
 	struct ttm_buffer_object *tbo;

drivers/gpu/drm/radeon/radeon_object.h

@@ -129,6 +129,7 @@ extern int radeon_bo_create(struct radeon_device *rdev,
 			    struct radeon_bo **bo_ptr);
 extern int radeon_bo_kmap(struct radeon_bo *bo, void **ptr);
 extern void radeon_bo_kunmap(struct radeon_bo *bo);
+extern struct radeon_bo *radeon_bo_ref(struct radeon_bo *bo);
 extern void radeon_bo_unref(struct radeon_bo **bo);
 extern int radeon_bo_pin(struct radeon_bo *bo, u32 domain, u64 *gpu_addr);
 extern int radeon_bo_pin_restricted(struct radeon_bo *bo, u32 domain,