T-API: changed optimal vector width for Intel

**Description:**
* changed optimal vector width for Intel platform since it shows better performance in most of cases

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2893/report/

check_regression=*OCL*AbsDiff*:*OCL*Add*:*OCL*Sub*:*OCL*Mul*:*OCL*Div*:*OCL*Bitwise*:*OCL*Compare*:*OCL*Min*:*OCL*Max*:*OCL*Flip*:*OCL*Repeat*:*OCL*AbsDiff*:*OCL*Sum*:*OCL*Count*:*OCL*Norm*:*OCL*Mean*:*OCL*CalcHist*
test_filter=*OCL*AbsDiff*:*OCL*Add*:*OCL*Sub*:*OCL*Mul*:*OCL*Div*:*OCL*Bitwise*:*OCL*Compare*:*OCL*Min*:*OCL*Max*:*OCL*Flip*:*OCL*Repeat*:*OCL*AbsDiff*:*OCL*Sum*:*OCL*Count*:*OCL*Norm*:*OCL*Mean*:*OCL*CalcHist*
test_modules=core,imgproc
build_examples=OFF