hwmon: lis3: pm_runtime support

Add pm_runtime support to lis3 core driver.
Add pm_runtime support to lis3 i2c driver.

spi and hp_accel drivers are not yet supported. Old always
on functionality remains for those.

For sysfs there is 5 second delay before turning off the
chip to avoid long ramp up delay.

Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>