As a first strep in introducing proper PAN management and association,
we need to be able to create coordinator interfaces which might act as
coordinator or PAN coordinator.

Hence, let's add the minimum support to allow the creation of these
interfaces.

Even though the necessary logic to handle several interfaces on the same
device is added to make this future move easier, in practice only
several interfaces of type MONITOR are allowed at the same time. The
other combinations are not allowed (interface creation is possible but
only one can be opened at a time) because, with a single PHY featuring a
single set of address filters, we cannot afford handling two distinct
interfaces (with different address filters or filtering requirements):
* Having 2 NODEs, 2 COORDs or 1 NODE + 1 COORD
  -> cannot work because the address filters would be different
* Having 1 MONITOR + either 1 NODE or 1 COORD
  -> cannot work because the filtering levels are incompatible
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20221026093502.602734-4-miquel.raynal@bootlin.comSigned-off-by: Stefan Schmidt <stefan@datenfreihafen.org>