Upgrade to fresh Linux release.
Enable more features in kernel from pmbootstrap kconfig check:
anbox, containers, iwd, nftables, zram.
Disable CONFIG_REGULATOR_DEBUG to reduce dmesg spam.
DRM and PANEL_SIMPLE are now built-in (DRM_MSM is still "m").
Switch to framebuffer from SIMPLEFB to tinydrm (SIMPLEDRM=y).
Switch APKBUILD to use "make zinstall" approach.
(Device packages might need small adjustments to initfs modules list.)
In preparation to removal of linux-postmarketos repo, switch
source to different source mirror.
I had to switch to gzip archive, because github doesn't serve bzip2.
I did a kconfig edit -> change nothing -> exit saving to regenerate config.
See also: postmarketos#47
[ci:skip-build] Already built fine on CI in MR
