arm-cci500: Rearrange PMU driver for code sharing with CCI-550 PMU

CCI-550 PMU shares most of the CCI-500 PMU attributes including the
event format, PMU event codes. The only difference is an additional
master interface (MI6 - 0xe). Hence we share the driver code for both,
except for a model specific event validate method.
This patch renames the common CCI500 symbols to CCI5xx, including the
Kconfig symbol.

No functional changes to the PMU driver.

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>