soc: fsl: dpio: add congestion notification support

Add support for Congestion State Change Notifications (CSCN), which
allow DPIO users to be notified when a congestion group changes its
state (due to hitting the entrance / exit threshold).

Acked-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

staging: fsl-mc: Move DPIO from staging to drivers/soc/fsl

Move the NXP DPIO (Datapath I/O Driver) out of the
drivers/staging directory and into the drivers/soc/fsl directory.

The DPIO driver enables access to Queue and Buffer Manager (QBMAN)
hardware on NXP DPAA2 devices. This is a prerequisite to moving the
DPAA2 Ethernet driver out of staging.

Signed-off-by: Roy Pledge <roy.pledge@nxp.com>
Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
Reviewed-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>