drm/gem-framebuffer: Test for imported buffers with drm_gem_is_imported()

Instead of testing import_attach for imported GEM buffers, invoke
drm_gem_is_imported() to do the test.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Anusha Srivatsa <asrivats@redhat.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250226172457.217725-7-tzimmermann@suse.de

Author: Thomas Zimmermann

drivers/gpu/drm/drm_gem_framebuffer_helper.c

@@ -429,7 +429,7 @@ static void __drm_gem_fb_end_cpu_access(struct drm_framebuffer *fb, enum dma_dat
 		if (!obj)
 			continue;
 		import_attach = obj->import_attach;
-		if (!import_attach)
+		if (!drm_gem_is_imported(obj))
 			continue;
 		ret = dma_buf_end_cpu_access(import_attach->dmabuf, dir);
 		if (ret)
@@ -466,7 +466,7 @@ int drm_gem_fb_begin_cpu_access(struct drm_framebuffer *fb, enum dma_data_direct
 			goto err___drm_gem_fb_end_cpu_access;
 		}
 		import_attach = obj->import_attach;
-		if (!import_attach)
+		if (!drm_gem_is_imported(obj))
 			continue;
 		ret = dma_buf_begin_cpu_access(import_attach->dmabuf, dir);
 		if (ret)