drm/amdkfd: Add mqd size in mqd manager struct

Also initialize mqd size on mqd manager initialization

Signed-off-by: Oak Zeng <ozeng@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>