drm/radeon: add proper checking of RESOLVE_BOX command for r600-r700

Checking of the second colorbuffer was skipped on r700, because
CB_TARGET_MASK was 0xf. With r600, CB_TARGET_MASK is changed to 0xff,
so we must set the number of samples of the second colorbuffer to 1 in order
to pass the CS checker.
The DRM version is bumped, because RESOLVE_BOX is always rejected without this
fix on r600.

Signed-off-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>