linux-postmarketos-grate: upgrade to 6.6.22

This upgrades kernel to 6.6.22 backporting fixes for major performance issues of Microsoft Surface RT.

This also re-generates config with "make grate_defconfig pmos.config" and adds pmb:kconfigcheck-uefi for surface rt.

Tested on surface rt, but it would be nice (however not necessary) to test it on other devices as well. Can be tested using mrtest from existing pmOS installations:

$ sudo apk add mrtest
$ mrtest add 4941

See https://wiki.postmarketos.org/wiki/Mrtest