amdgpu_framebuffer doesn't have tiling_flags, so we need this.

amdgpu_display_get_fb_info never gets NULL parameters, so checking for NULL
was useless.
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>