media: i2c: imx290: Explicitly set v&h blank on mode change

__v4l2_ctrl_modify_range only updates the current value should
it be invalid within the new range. That can leave modes producing
odd frame rates.

Explicitly update the HBLANK and VBLANK values so that on mode
change we revert to the default frame rate for the mode.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>