add utest for llvm intrinsic call usub_with_overflow funtion.

add utest for llvm intrinsic call usub_with_overflow funtion.

as llvm couldn't recognize the pattern of usub overflow, this usub
with is generated by calling the intrinsic function __builtin_usub_overflow;
also this type of uadd intrinsic funtion couldn't support short/byte type
overflow, we choose another way for the uadd kernel to generate short/byte
overflow.
will send patch to llvm later to fix the 2 issues.

v2: split the patch.

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