coresight: add PM runtime calls to coresight_simple_func()

It is mandatory to enable a coresight block's power domain before
trying to access management registers.  Otherwise the transaction
simply stalls, leading to a system hang.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>