cxgb4: Print adapter VPD Part Number instead of Engineering Change field

When we attach to adapter, print VPD Part Number instead of Engineering Change field.
Based on original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Kumar Sanghvi <kumaras@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>