coresight: enable clocks during hotplug when required

Vote for enabling clocks during hotplug ON in CPU_UP_PREPARE and
correspondingly vote to disable clocks in CPU_ONLINE or
CPU_UP_CANCELED callbacks until OS lock is unlocked. This is
required since memory mapped accesses to unlock the OS lock as
part of CPU_STARTING callback for some ARM based cpus need the
appropriate clocks to be on.

Change-Id: Ia9709692beb02654c225a0771c1eea556d581372
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>