arm-cci: CoreLink CCI-550 PMU driver

Add ARM CoreLink CCI-550  cache coherent interconnect PMU
driver support. The CCI-550 PMU shares all the attributes of CCI-500
PMU, except for an additional master interface (MI-6 - 0xe).
CCI-550 requires the same work around as for CCI-500 to
write to the PMU counter.

Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Punit Agrawal <punit.agrawal@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>