On some board it is possible that the sensor 'powerdown' and or 'reset'
pin might be controlled by gpio instead of being tied.

To implement we add pm_runtime support which will handle the power
up/down sequence when it is available otherwise the sensor will be
powered on at module insertion/probe and powered off at module removal.

Now originally the driver assumed that the sensor would always stay
powered and keep its register setting. We cannot assume this anymore, so
every time we "power up" we need to re-program the initial registers
configuration first. This was previously done only at probe time.

[Sakari Ailus: Resolve a conflict in Kconfig]
Signed-off-by: Benoit Parrot <bparrot@ti.com>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>