release: v4.20-pf1

* the kernel has been rebased to v4.20;
* the PDS-mq CPU scheduler v0.99i has been merged along with pending
fix;
* UKSM has been forward-ported from v4.19;
* graysky's CPU optimisations patch has been applied;
* the memstick power management patchsed has been applied;
* minor BFQ comment fix has been cherry-picked;
* Arch CLONE_NEWUSER patch has been applied;
* mangled DSDT support for Dell Vostro 3360 laptop has been merged.
This tag has no release notes.