Add the support for 1D image in backend

Add the support for 1D image in backend

1. Delete the is3D member in instruction class. Because we need more
than 1 bit to represent 1D 2D and 3D. We now add an invalid register
in ir profile, and comparing the coords to it to judge the dimension.
2. Rename all the xxx_image to xxx_image2D to make its meaning clear.
3. Update the according Sampler and Typed_Write instruction in selection
and Gen IR generation.

v2:
fix the use of InvalidRegister. Use ir::ocl::invalid only.

Signed-off-by: Junyan He <junyan.he@linux.intel.com>
Signed-off-by: Zhigang Gong <zhigang.gong@intel.com>