Currently only 256 vports can be supported as only 8 bits are
reserved for them and 8 bits are reserved for vhca_ids in
metadata reg c0. To support more than 256 vports, replace
vhca_id with a unique shorter 4-bit PF number which covers
upto 16 PF's. Use remaining 12 bits for vports ranging 1-4095.
This will continue to generate unique metadata even if
multiple PCI devices have same switch_id.