ACPI/PCC: Add maintainer for PCC mailbox driver

Not much functionality is added since PCC driver was added 5 years ago.
There is need to restructure the driver while adding support for PCC
Extended subspaces type 3&4. There is more rework needed as more users
adopt PCC on arm64 platforms. In order to ease the same, I would like
to take responsibility to maintain this driver.

Acked-by: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>