arm64: perf: add support for Cortex-A73

The Cortex-A73 uses some implementation defined perf events.

This patch sets up the necessary mapping for Cortex-A73.

Mappings are based on Cortex-A73 TRM r0p2, section 11.9 Events
(pages 11-457 to 11-460).

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>