drm/amdkfd: Rename kfd_kernel_queue_*.c to kfd_packet_manager_*.c

After the recent cleanup, the functionalities provided by the previous
kfd_kernel_queue_*.c are actually all packet manager related. So rename
them to reflect that.

Signed-off-by: Yong Zhao <Yong.Zhao@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>