drm/amdgpu: change gartsize default to 256MB

Limit the default GART size and save a lot of VRAM.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c7436ea4..019a4b7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -75,7 +75,7 @@
  */
 extern int amdgpu_modeset;
 extern int amdgpu_vram_limit;
-extern int amdgpu_gart_size;
+extern unsigned amdgpu_gart_size;
 extern int amdgpu_gtt_size;
 extern int amdgpu_moverate;
 extern int amdgpu_benchmarking;