perf/dwc_pcie: Support counting multiple lane events in parallel

While Designware PCIe PMU allows to count only one time based event
at a time, it allows to count all the lane events simultaneously.
After the patch one is able to count a group of lane events:

  $  perf stat -e '{dwc_rootport/tx_memory_write,lane=1/,dwc_rootport/rx_memory_read,lane=0/}' dd if=/dev/nvme0n1 of=/dev/null bs=1M count=1

Earlier the events wouldn't have been counted successfully.

Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Signed-off-by: Will Deacon <will@kernel.org>