We currently hard code the maximum number of ports in the driver, but
this may change in future devices, so query it from the firmware
instead.

Fallback to a maximum of 64 ports in case this number can't be queried.
This should only happen in SwitchX-2 for which this number is correct.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>