drm/amdgpu/gmc: disable keep_stolen_vga_memory on arcturus

I suspect the only reason this was set was to avoid touching
the display related registers on arcturus.  Someone should
double check this on arcturus with S3.
Reviewed-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c

@@ -448,7 +448,6 @@ void amdgpu_gmc_get_vbios_allocations(struct amdgpu_device *adev)
 	switch (adev->asic_type) {
 	case CHIP_VEGA10:
 	case CHIP_RAVEN:
-	case CHIP_ARCTURUS:
 	case CHIP_RENOIR:
 		adev->gmc.keep_stolen_vga_memory = true;
 		break;