drm/amdkfd: fix runlist length calculation

The MAP_QUEUES packet length for Carrizo is different than for Kaveri.
Therefore, we now need to calculate the runlist length with regard to the
underlying H/W.

Signed-off-by: Ben Goz <ben.goz@amd.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>