net: dsa: introduce new DSA framework

The new DSA framework purpose and changes are as below.

- Aligned to Linux DSA framework which has been already mature framework
  for many years, For now in zephyr, the DSA components were splited
  as: switch, port, master(not need driver file for now), slave, and tag.
  Seperated drivers were used for maintaining and developing new
  features.

- The unified dts bindings (aligned to linux) were supported. The port
  driver would parse DTS to decide the port type (master port, slave
  port, or cpu port) to set up the switch. All the ports registered as
  standard ethernet devices. (dsa port and dsa switch tree was not
  supported.)

- How to add DSA device driver based on the framework? All the device
  driver needing to do is providing dsa_spi implementation and private
  data, and calling below initialization.

    DSA_INIT_INSTANCE(n, _dapi, data)

- For switch tag case, recv/xmit helpers in dsa_api could be used for
  taging/untagging. No modified ethernet drivers.
  For no-tag type case, ethernet driver of master port should support
  packet injection/extraction for slave ports leaving NULL recv/xmit.

The dsa_nxp_imx_netc.c driver will be the first example of the new DSA
framework.

The future work for DSA will be supporting bridge for ports. We may align
Linux to give users two options to use DSA device:

- Standalone mode: the switch ports work as regular ethernet ports.

- Bridge mode: switch mode with virtual bridge device which could be
  assigned IP address.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>