linux-postmarketos-allwinner: Upgrade to 5.12.6 (MR 2149)

I rebased all of the patches (only 2 needed some changes, the rest I
just did for good measure).

These two patches were dropped since they are already merged in the new
kernel:
        0008-leds-gpio-Set-max-brightness-to-1.patch
        0009-dts-pinephone-Add-pine64-pinephone-to-compat-list.patch was dropped

The kconfig changes are just after running kconfig edit, and making no
changes so that it would generate a config with any new options in 5.12,
to make maintenance easier moving forward.