arm-cci: Sanitise CCI400 PMU driver specific code

Rename CCI400 specific defintions from CCI_xxx to CCI400_xxx.

Introduce generic ARM_CCI_PMU to cover common code for handling
the CCI PMU.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Acked-by: Punit Agrawal <punit.agrawal@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>