drivers: media: i2c: imx219: Fix for imx219_get_binning()

[njhollinghurst]

Fixes 5eb74d4 ("Remove enum binning_mode")
which mixed two different interpretations of "bin_h", "bin_v" (as binning factors and as binning modes), and broke binning.

In this version they are factors; the return value is the selected binning mode (which also depends on the sensor mode).

[njhollinghurst]

Candidate fix for #7391

[njhollinghurst]

There remains some redundancy in imx219_set_pad_format() which

• computes binning factors itself
• calls imx219_get_binning()
• calls imx219_get_rate_factor() which again calls imx219_get_binning()

but perhaps that's not urgent to fix.

[6by9]

Do just check the patches off mainline for duplication.
https://github.com/torvalds/linux/commits/master/drivers/media/i2c/imx219.c

Sakari's patchset at https://lore.kernel.org/linux-media/20260408153939.969381-1-sakari.ailus@linux.intel.com/ is also messing with imx219, and I'm reviewing those patches at the moment.

[njhollinghurst]

Hmm. The above is the minimal fix to unbreak what we have now.
In mainline the imx219_get_binning() function continues to return void. Maybe we should stay closer to that.

The thing we need to bring in that's absent from mainline, is the sensor-mode-dependent binning method, from 82ffe96

I'll have another go...

[6by9]

Upstream, Jai has increased the LLP slightly, and that has fixed the need for different binning modes. Those should have been in 6.15 and above, so I'm not sure there is a need any longer.

[njhollinghurst]

Will start again by reverting downstream changes...