drm/amdgpu: change reserved vram info print

The link object of mgr->reserved_pages is the blocks
variable in struct amdgpu_vram_reservation, not the
link variable in struct drm_buddy_block.

Signed-off-by: YiPeng Chai <YiPeng.Chai@amd.com>
Reviewed-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org