dt-bindings: display: imx: Add i.MX8qxp Display Controller AXI performance counter

i.MX8qxp Display Controller contains a AXI performance counter which allows
measurement of average bandwidth and latency during operation.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250414035028.1561475-6-victor.liu@nxp.com