drm/amd/powerplay: implement smu_alloc[free]_memory pool function

This patch implements smu_alloc[free]_memory pool function to reserve the memory
pool bo.

Signed-off-by: Kevin Wang <Kevin1.Wang@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>