media: staging: atomisp: Remove ->power_ctrl() callback

There is redundant callback which does nothing in upstreamed version of
the driver.

Remove it along with user call places.

Mostly done with help of coccinelle.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>