pwm: lpss: Update PWM setting for Broxton

pwm: lpss: Update PWM setting for Broxton

BugLink: http://bugs.launchpad.net/bugs/1520436
For Broxton PWM controller, base unit is defined as 8-bit integer
and 14-bit fraction, so need to update base unit setting to output
wave with right frequency.

Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit 883e4d070fe125028c0579d8666b820aadf458fb)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>