linux-postmarketos-qcom-msm8994: upgrade 6.12

Patch adding LG G4 (H815) support got upstreamed in v6.12-rc1 mainline kernel (it's slightly different than the patch used here).

Add python3 to makedepends (required from v6.10-rc1 0fddd045f88e ("drm/msm: generate headers on the fly")).

Signed-off-by: Petr Vorel pvorel@suse.cz # part of https://hackweek.opensuse.org/