Use more unrolling for scaled src_0565_0565 with nearest filter

Use more unrolling for scaled src_0565_0565 with nearest filter

Benchmark from Intel Core i7 860:

    == before ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=1335.29 MPix/s

    == after ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=1550.96 MPix/s

    == performance of nonscaled src_0565_0565 operation as a reference ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=2401.31 MPix/s

Benchmark from ARM Cortex-A8:

    == before ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=81.79 MPix/s

    == after ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=89.55 MPix/s

    == performance of nonscaled src_0565_0565 operation as a reference ==
    op=1, src_fmt=10020565, dst_fmt=10020565, speed=197.44 MPix/s