UNTESTED fix for libcamera0.7

[AndrolGenhald]

Fixes #206 (maybe).

I want to be very clear about this: I did not test this, I do not even really know how to test this feature.

All I did was take the code from libcamera_device_apply_controls and more-or-less copy/paste it here with the variables changed so that it updates the existing controls instead of overwriting them. This fixes the error and I can now stream video with libcamera0.7, but as far as I know I don't rely on this feature and I could have just commented out line 83 and it would work just as well for me.

[mryel00]

Fyi #205 is tested and fixes the error. The PR title is not optimal, I should maybe adjust it ^^

[AndrolGenhald]

Oh, awesome! I searched issues for "libcamera0.7" but apparently I forgot to search PRs. I'll close this in favor of #205 then.

[mryel00]

I looked again in more depth into the libcamera code. Seems like my code will not always overwrite existing controls, as I didn't check the default values 😅
https://github.com/raspberrypi/libcamera/blob/1e2272178fa317ad3e1931a608d4d54d9c649db6/include/libcamera/controls.h#L435

Your PR, and therefore libcamera_device_apply_controls, seem to just copy the behavior of the merge operation I used:
https://github.com/raspberrypi/libcamera/blob/1e2272178fa317ad3e1931a608d4d54d9c649db6/src/libcamera/controls.cpp#L995-L1036

So thank you for this PR, so I could spot my error.