pwm: lpss: remove dependency on clk framework

Unlike other Intel LPSS devices, the PWM does not have the
clock dividers or the gate. All we get from the clock is the
rate. Since PCI case uses the driver data to get the rate,
we can drop the clk and use the same data also in case of
ACPI. The frequency is the same.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Chew, Chiau Ee <chiau.ee.chew@intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>