media: i2c: imx219: Balance runtime PM use-count

Move incrementing/decrementing runtime PM count to
imx219_start_streaming()/imx219_stop_streaming() functions respectively.

This fixes an issue of unbalanced runtime PM count in resume callback
error path where streaming is stopped and runtime PM count is left
unbalanced.

Fixes: 1283b3b8 ("media: i2c: Add driver for Sony IMX219 sensor")
Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>