fix piglit get kernel info FUNCTION ATTRIBUTE fail.

fix piglit get kernel info FUNCTION ATTRIBUTE fail.

the backend need return the kernel FUNCTION ATTRIBUTE message to the
clGetKernelInfo.
there are 3 kind of function attribute so far, vec_type_hint parameter
is not available to return due to llvm lack of such info.

Signed-off-by: Luo <xionghu.luo@intel.com>
Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>