media: i2c: imx290: Fix clock setup register assignments

When the clock setups were added for the alternate external clocks,
the settings for 2 lane 720p and 4 lane 1080p were transposed.
2 lane 720p still worked, but 4 lane 1080p didn't.

Correct the assignments.

Fixes: 6b0c094a (media: i2c: imx290: Add support for 74.25MHz clock")

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