[media] v4l: mt9v032: Do not unset master_mode

The power_on function of the driver resets the chip and sets the
CHIP_CONTROL register to 0. This switches the operating mode to slave.
The s_stream function sets the correct mode. But this caused problems on
a board where the camera chip is operated as master. The camera started
after a random amount of time streaming an image, I observed between 10
and 300 seconds.

The STRFM_OUT and STLN_OUT pins are not connected on this board which
may cause some issues in slave mode. I could not find any documentation
about this.

Keeping the chip in master mode after the reset helped to fix this
issue for me.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>