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>

MAINTAINERS

@@ -401,6 +401,12 @@ L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
 F:	drivers/platform/x86/i2c-multi-instantiate.c
 
+ACPI PCC(Platform Communication Channel) MAILBOX DRIVER
+M:	Sudeep Holla <sudeep.holla@arm.com>
+L:	linux-acpi@vger.kernel.org
+S:	Supported
+F:	drivers/mailbox/pcc.c
+
 ACPI PMIC DRIVERS
 M:	"Rafael J. Wysocki" <rafael@kernel.org>
 M:	Len Brown <lenb@kernel.org>