media: imx: imx-mipi-csis: Drop powered flag

The mipi_csis_device.powered flag only serves for the purpose of
not accessing registers in mipi_csis_log_status() when the interface
is not powered up.

Instead of manually tracking the power state, rely on
pm_runtime_get_if_in_use() to remove the 'powered' flag. Also remove
the locking in the function as runtime_pm() is refcounted and there's no
risk of the interface being powered down behind our backs.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>