Merge branch 'net-dsa-turn-arrays-of-ports-into-a-list'

Vivien Didelot says:

====================
The dsa_switch structure represents the physical switch device itself,
and is allocated by the driver. The dsa_switch_tree and dsa_port structures
represent the logical switch fabric (eventually composed of multiple switch
devices) and its ports, and are allocated by the DSA core.

This branch lists the logical ports directly in the fabric which simplifies
the iteration over all ports when assigning the default CPU port or configuring
the D in DSA in drivers like mv88e6xxx.

This also removes the unique dst->cpu_dp pointer and is a first step towards
supporting multiple CPU ports and dropping the DSA_MAX_PORTS limitation.

Because the dsa_port structures are not tied to the dsa_switch structure
anymore, we do not need to provide an helper for the drivers to allocate a
switch structure. Like in many other subsystems, drivers can now embed their
dsa_switch structure as they wish into their private structure. This will
be particularly interesting for the Broadcom drivers which were currently
limited by the dynamically allocated array of DSA ports.

The series implements the list of dsa_port structures, makes use of it,
then drops dst->cpu_dp and the dsa_switch_alloc helper.
====================

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>