drivers/perf: Remove ARM_SPE_PMU explicit PERF_EVENTS dependency

Since commit bddb9b68

 ("drivers/perf: commonise PERF_EVENTS
dependency"), all perf drivers depend on PERF_EVENTS config under a
common menu.

Config ARM_SPE_PMU still declares explicitly a dependency on
PERF_EVENTS, which is unneeded, so remove it.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>