OCL: pyrUp

**Description:**
- unrolled kernel for 1-channel
- removed storing of zeros and multiplication by them

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2790/report/

check_regression=*OCL*yrUp*
build_examples=OFF
test_modules=imgproc
`dst.rows` and `dst.cols` are always even for current implementation.