avcodec/dsputil: fix signedness in sizeof() comparissions

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
void ff_put_rv40_qpel8_mc33_c(uint8_t *dst, uint8_t *src, ptrdiff_t stride)
{
    put_pixels8_xy2_8_c(dst, src, stride, 8);
}

void ff_put_rv40_qpel8_mc33_c(uint8_t *dst, uint8_t *src, ptrdiff_t stride)
{
    put_pixels8_xy2_8_c(dst, src, stride, 8);
}
