drm/radeon: fix amd afusion gpu setup aka sumo v2

Set the proper number of tile pipe that should be a multiple of
pipe depending on the number of se engine.

Fix:
https://bugs.freedesktop.org/show_bug.cgi?id=56405
https://bugs.freedesktop.org/show_bug.cgi?id=56720



v2: Don't change sumo2

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>