drm/amd/powerplay: implement smu_init(fini)_fb_allocations function

This patch implements smu_init_fb_allocations/smu_fini_fb_allocations function
for smu to reserve the BOs for smc tables.

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>