ARC: perf: trivial code cleanup

* Use BIT(), lower_32_bits(), upper_32_bits() macroses,
  fix code style violations.
* Use u32, u64, s64 instead of uint32_t, uint64_t, int64_t
* Fix description comment as this code doesn't belong only to
  ARC700 anymore.
* Use SPDX License Identifier.
* Remove useless ifdefs. ifdef around 'arc_pmu_match' structure
  declaration is useless as we refer to 'arc_pmu_match' in
  several places which aren't guarded with ifdef. Nevertheless
  'ARC' option selects 'OF' unconditionally so we can simply
  get rid of this ifdef.

Acked-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>