net: dsa: sja1105: dimension the data structures for a larger port count

Introduce a SJA1105_MAX_NUM_PORTS macro which at the moment is equal to
SJA1105_NUM_PORTS (5). With the introduction of SJA1110, these
structures will need to hold information for up to 11 ports.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>