drm/amd/pp: fix "Delete the wrapper layer of smu_allocate/free_memory"

For amdgpu_bo_create_kernel to work the handle must be NULL initialized,
otherwise we only try to pin and map the BO.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Rex Zhu <rezhu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>