platform/x86: Add Whiskey Cove PMIC TMU support

This adds TMU (Time Management Unit) support for Intel BXT platform.
It enables the alarm wake-up functionality in the TMU unit of Whiskey Cove
PMIC.

Signed-off-by: Nilesh Bacchewar <nilesh.bacchewar@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
[andy: resolve merge conflict in Kconfig]
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>