mfd: Set asic3 DS1WM clock_rate

The mfd/asic3 driver does not set the ds1wm_driver_data clock_rate field
before passing the structure to the DS1WM w1 busmaster driver.
This was not noticed before commit 26a6afb9

, because ds1wm_find_divisor()
unintentionally returned the correct divisor when a zero clock_rate was
passed in. However after that commit DS1WM fails a zero clock_rate:

ds1wm ds1wm: no suitable divisor for 0Hz clock

This patch sets the ds1wm_driver_data clock_rate field.

Signed-off-by: Paul Parsons <lost.distance@yahoo.com>
Acked-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>