coresight: add support for coresight hardware event driver

The STM hardware event interface allows monitoring and tracing
of up to 32 hardware events. The CoreSight Hardware Event driver
programs various hardware event mux control registers to configure
these hardware events based on user selection. Currently APSS
controlled hardware event configurations are supported.

Change-Id: Ic2749ae1a8d405159cc7e8210dfc1d8864f96df9
Signed-off-by: Aparna Das <adas@codeaurora.org>