Merge kselftest from Linux 4.20

This merges in kselftest from Linux 4.20, or upstream commit
8fe28cb5.

New test suites include cgroup, kvm, netfilter, proc, rseq, and rtc. New
tests applicable to Android are not yet enabled.

The efivarfs and net/psock_tpacket tests now return a proper skip code
instead of 0 when a skip condition is encountered. Due to current
limitations in the VTS kselftest harness these tests must be disabled.

Test: run vts-kernel -m VtsKernelLinuxKselftest
Bug: 79702574
Change-Id: If71266ff1e514c6bf6015de6c8a0bc4aaa256249
Signed-off-by: Steve Muckle <smuckle@google.com>