Enable hardware perf-events if CPU_HAS_PMU and select
HAVE_OPROFILE if HAVE_PERF_EVENTS. If no hardware support
is present, OProfile will fall back to timer mode.

This patch also removes the old OProfile drivers in favour
of the code implemented by perf.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>