Add delay to coefficient loader fix.

I thought the time taken to read back and then write zero back to the
DAP_FILTER_COEF_ACCESS WR bit would be enough but coefficients did not
load to the selected filter, tried 1ms delay instead still didn't work -
chances are that either not zero-ing or only zero-ing just before
writing the DAP_COEF_WR_xx_xSB registers would be fine but for now I'd
prefer to zero it sooner than later.