Fix map gtt fail when memory object size is too large.

Fix map gtt fail when memory object size is too large.

After max allocate size is changed to 256M, the large memory object would map gtt
fail  in some system. So when image size is large then 128M, disable tiling, and
used normal map. But in function clEnqueueMapBuffer/Image, may still fail because
unsync map.

Signed-off-by: Yang Rong <rong.r.yang@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>