[infiniband] Change IB_{QPN,QKEY,QPT} names from {SMA,GMA} to {SMI,GSI}

[infiniband] Change IB_{QPN,QKEY,QPT} names from {SMA,GMA} to {SMI,GSI}

The IBA specification refers to management "interfaces" and "agents".
The interface is the component that connects to the queue pair and
sends and receives MADs; the agent is the component that constructs
the reply to the MAD.

Rename the IB_{QPN,QKEY,QPT} constants as a first step towards making
this separation in gPXE.