main/linux-postmarketos-grate: upgrade to 5.14.0_rc6, introduce new config

Changes in kernel package:

• Update to 5.14.0_rc6;
• support for WiFi (contributed by @jenneron) and battery (contributed by CrackTheSurface) for Microsoft Surface RT;
• transformers and chagall clean up (contributed by @clamor95);
• cleaner config;
• zImage now is 3.0M, so it should be able to boot on asus-grouper (its bootloader accepts < 3.5M zImage) and probably other devices with bootloader limitations.

Changes in device packages:

• initfs modules for display, touchscreen, keyboard and battery for all related devices (these features were built-in before);
• Microsoft Surface RT nonfree firmware for WiFi;
• use linux-postmarketos-grate package for asus-grouper.

For now there is an issue with osk-sdl, it prints incorrect passphrase for correct one. Someone else should test it as surface does not have a peripheral USB port to open a debug-shell, so i can't test it myself. Also i don't have an asus-grouper, i tested it only with Microsoft Surface RT. This MR should be tested on all devices as i could miss some modules.

For testers:

1. Checkout to this branch;
2. Build new pmOS installation with enabled debug-shell;
3. Boot and connect via telnet; make sure that display, touchscreen, battery and keyboard if present work. Use evtest tool in debug-shell and check /sys/class/power_supply.
4. Type pmos_continue_boot in debug-shell to boot rootfs and test everything else.

TODO:

• fix FDE;
• test microsoft-surface-rt;
• test asus-tf201;
• test asus-tf300t;
• test asus-tf700t;
• test pegatron-chagall;
• test acer-picasso.