drm/amdgpu: avoid reading vf2pf info size from FB

VF can't access FB when host is doing mode1 reset. Using sizeof to get
vf2pf info size, instead of reading it from vf2pf header stored in FB.
Signed-off-by: Zhigang Luo <Zhigang.Luo@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -585,7 +585,7 @@ static int amdgpu_virt_write_vf2pf_data(struct amdgpu_device *adev)
 	}
 	vf2pf_info->checksum =
 		amd_sriov_msg_checksum(
-		vf2pf_info, vf2pf_info->header.size, 0, 0);
+		vf2pf_info, sizeof(*vf2pf_info), 0, 0);
 
 	return 0;
 }