media: i2c: imx290: VMAX is mode dependent

The default VMAX for 60fps in 720p mode is 750 according to the
datasheet, however the driver always left it at 1125 thereby stopping
60fps being achieved.

Make VMAX (and therefore V4L2_CID_VBLANK) mode dependent so that 720p60
can be achieved.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>