tools/fuzz: Add a cpu-policy fuzzing harness

tools/fuzz: Add a cpu-policy fuzzing harness

There is now enough complexity that a fuzzing harness is a good idea, and
enough supporting logic to implement one which AFL seems happy with.

Take the existing recalculate_synth() helper and export it as
x86_cpuid_policy_recalc_synth(), as it is needed by the fuzzing harness.

While editing the MAINTAINERS file, insert a related entry which was
accidentally missed from c/s 919ddc3c0 "tools/cpu-policy: Add unit tests", and
sort the lines.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>