coresight: turn on pcsave during first hotplug if enabled in boot

When PC save is enabled via kernel command line or config item
but we boot with maxcpus parameter value of less than number of
present cpus, cpus that are not included as part of maxcpus don't
get PC save feature enabled during kernel init since those cpus
would not be online.

This change ensures that for such cpus, first hotplug after the
respective cpu's ETM probe is done, enables PC save feature if
the feature is enabled via kernel command line or config item but
hasn't already been enabled.

Change-Id: I9cae33654539ed72885fdf11cd603c7c776512c1
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>