ARM: perf: add support for the Cortex-A15 PMU

This patch adds support for the Cortex-A15 PMU to the ARMv7
perf-event backend.

Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --cc arch/arm/include/asm/perf_event.h
Simple merge

diff --cc arch/arm/kernel/perf_event.c
Simple merge

diff --cc arch/arm/kernel/perf_event_v7.c
Simple merge