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

This reverts commit 090d29f5.

Whilst the behaviour of not resetting the frame rate to the
"correct"/default value on mode change is useful, it is not correct
under the V4L2 API.

Revert the patch so that blanking values persist.

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