MLK-25346: net: add imx-shmem-net driver

MLK-25346: net: add imx-shmem-net driver

This driver uses the shared memory and the mailbox units to
provide a virtual network interface toward a peer device on
the same SoC. This new driver is based on ivshmem-net driver,
where we replace ivshmem's registers by struct 'regs' in the
context, and push in MU all modifications to 'regs' value lstate.

FEATURES:
Only 2 identical devices in different HW partitions and connected
by an MU can talk to each other.
All MU transaction may timeout: if first message sent through MU,
then the driver will be probed again.
The driver supports peer's partition reset:
driver registers to SCFW service to receive a notification when
peer's partition resets.
The driver supports multiple devices
(i.e. multiple connections to different partitions).

Signed-off-by: Seb Fagard <sebastien.fagard@nxp.com>
Signed-off-by: Nitin Garg <nitin.garg@nxp.com>
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>