staging: clocking-wizard: Add support for fractional support

Currently the set rate granularity is to integral divisors.
Add support for the fractional divisors.
Only the first output0 is fractional in the hardware.

Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Link: https://lore.kernel.org/r/1614172241-17326-7-git-send-email-shubhrajyoti.datta@xilinx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>