perf: arm_pmuv3: Don't disable counter in armv8pmu_enable_event()

perf: arm_pmuv3: Don't disable counter in armv8pmu_enable_event()

Currently armv8pmu_enable_event() starts by disabling the event counter
it has been asked to enable. This should not be necessary as the counter
(and the PMU as a whole) should not be active when
armv8pmu_enable_event() is called.

Remove the redundant call to armv8pmu_disable_event_counter(). At the
same time, remove the comment immeditately above as everything it says
is obvious from the function names below.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20250218-arm-brbe-v19-v20-3-4e9922fc2e8e@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>