[linux-postmarketos] Update to 4.13
NOTE: This updates linux-postmarketos from 4.12.x to 4.13.
Please test thoroughly!
An initial smoke test in QEMU and on my N900 passed, I was able to boot up, get networking, and poweroff.
Also, I do not have a device with aarch64, so I did not generate a config for this or test it.. if someone is able to test then I can create a config by accepting the defaults.