linux-postmarketos-qcom-msm8226: upgrade to 6.8.7 (+ a bit more)

And "firmware-htc-memul: un-squash wcnss firmware"

Useful command for testing: cpufreq-info -m from cpufrequtils package, also running unixbench (see wiki) with powersave and performance governor should show significant difference. Benchmark results could be lower though than without this MR as speedbin is not implemented yet, so max. frequency could be slighly lower than bootloader-initialized frequency I think.