driver/perf: Add PMU driver for the ARM DMC-620 memory controller

DMC-620 PMU supports total 10 counters which each is
independently programmable to different events and can
be started and stopped individually.

Currently, it only supports ACPI. Other platforms feel free to test and add
support for device tree.

Usage example:
  #perf stat -e arm_dmc620_10008c000/clk_cycle_count/ -C 0
  Get perf event for clk_cycle_count counter.

  #perf stat -e arm_dmc620_10008c000/clkdiv2_allocate,mask=0x1f,match=0x2f,
  incr=2,invert=1/ -C 0
  The above example shows how to specify mask, match, incr,
  invert parameters for clkdiv2_allocate event.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Tuan Phan <tuanphan@os.amperecomputing.com>
Link: https://lore.kernel.org/r/1604518246-6198-1-git-send-email-tuanphan@os.amperecomputing.com


Signed-off-by: Will Deacon <will@kernel.org>