drm/amdkfd: Make deallocate_hiq_sdma_mqd static

Fix sparse warning:

drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_device_queue_manager.c:1846:6:
 warning: symbol 'deallocate_hiq_sdma_mqd' was not declared. Should it be static?

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>