dmaengine: idxd: Clean up cpumask and hotplug for perfmon

The idxd PMU is system-wide scope, which is supported by the generic
perf_event subsystem now.

Set the scope for the idxd PMU and remove all the cpumask and hotplug
codes.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20240802151643.1691631-6-kan.liang@linux.intel.com