drivers: media: imx708: Adjust broken line correction parameter

In full-resolution mode, the LPF_INTENSITY_EN and LPF_INTENSITY
registers control Quad Bayer Re-mosaic broken line correction.
Expose this as a module parameter "qbc_adjust": zero disables
the correction and values in the range 2 to 5 set its strength.

There is a trade-off between coloured and monochrome patterns.
The previous fixed value 4 could produce ladder/spots artefacts
in coloured textures. The new default value 2 may suit a wider
range of scenes.

Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>