arm: perf: Disable IRQs when reading a counter

pmu->read() can be called with interrupts enabled and it ends up calling
armv7pmu_read_counter() from armpmu_event_update(). The IRQ handler also
calls armpmu_event_update(). If we get an interrupt after
armv7pmu_read_counter() programs the counter selection register, but before
reading the counter value, we can end up reading the wrong register value
after the interrupt, because the handler re-programmed the counter selection
register.

Disable IRQs when reading the counter to prevent this from happening.

Reported-by: Julien Thierry <julien.thierry@arm.com>
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: stable@vger.kernel.org