ASoC: RX1950: Fix hw_params function

Unfortunatelly, I misunderstood datasheet, and on s3c244x-iis
when MPLLin source for master clock is selected, prescaler has
no effect. Remove dividor calculation for 44100 rate; remove 88200
rate at all, rx1950 can't do it.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>