arm64: perf: Move event definitions into perf_event.h

The PMU event numbers are split between perf_event.h and perf_event.c,
which makes it difficult to spot any gaps in the numbers which may be
allocated in the future.

This patch sorts the events numerically, adds some missing events and
moves the definitions into perf_event.h.

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