drm/ttm: fix incrementing the page pointer for huge pages

When we increment the counter we need to increment the pointer as well.

Signed-off-by: Christian König <christian.koenig@amd.com>
Fixes: e16858a7e6e7 drm/ttm: fix start page for huge page check in ttm_put_pages()
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>