In preparation for support of new eHCA2 features, change adapter probing:
 - Hardware level is changed to encode major and minor chip version
 - Hardware capabilities are queried from the firmware
 - The maximum MTU is queried from the firmware instead of assuming a
   fixed value
Signed-off-by: NJoachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>