The out-of-band tick device manages the timer hardware by interposing
on selected clockevent handlers transparently, so that a client domain
(e.g. a co-kernel) eventually controls such hardware for scheduling
the high-precision timer events it needs to. Those events are
delivered to out-of-hand activities running on the head stage,
unimpeded by (only virtually) interrupt-free sections of the regular
kernel code.

This commit introduces the generic API for controlling the out-of-band
tick device from a co-kernel. It also provides for the internal API
clock event chip drivers should use for enabling high-precision
timing for their hardware.