drivers: i2s: intel_s1000: Fractional bit-clock

Added support for fractional division of reference clock to obtain
I2S bit clocks
For example:
    If reference clock is 38.4MHz and
    if the I2S format is 2ch, 32bits per channel, 48KHz sample rate,
    the bit clock frequency has to be 2*32*48K = 3.072MHz
    38.4MHz/3.072MHz = 12.5 (a fraction)

Signed-off-by: Sathish Kuttan <sathish.k.kuttan@intel.com>