iio: accel: kxcjk-1013: support runtime pm

In an effort to improve raw read performance and at the same time enter
low power state at every possible chance.
For raw reads, it will keep the system powered on for a default or user
specified time, via autosuspend_delay attribute of device power.
This will help read multiple samples without power on/off sequence.
For triggers it will keep the system on till, requested to be turned
off by trigger state by utilizing run time PM usage counters.

When runtime pm is not enabled, then it keeps the chip in operation
mode always.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>