drm/amdkfd: Remove initialization of cp_hqd_ib_control on CIK

The initialization is not necessary. amd-kfd-staging and ROCm
releases have worked without it for two years.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>