drivers/bus: Split Arm CCI driver

The arm-cci driver is really two entirely separate drivers; one for MCPM
port control and the other for the performance monitors. Since they are
already relatively self-contained, let's take the plunge and move the
PMU parts out to drivers/perf where they belong these days. For non-MCPM
systems this leaves a small dependency on the remaining "bus" stub for
initial probing and discovery, but we end up with something that still
fits the general pattern of its fellow system PMU drivers to ease future
maintenance.

Moving code to a new file also offers a perfect excuse to modernise the
license/copyright headers and clean up some funky linewraps on the way.

Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com>
Acked-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>