drivers/perf: arm_pmu: Fix failure path in PM notifier

Handling of the CPU_PM_ENTER_FAILED transition in the Arm PMU PM
notifier code incorrectly skips restoration of the counters. Fix the
logic so that CPU_PM_ENTER_FAILED follows the same path as CPU_PM_EXIT.

Cc: <stable@vger.kernel.org>
Fixes: da4e4f18 ("drivers/perf: arm_pmu: implement CPU_PM notifier")
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>