cxgbe(4): fix the size of the iq/eq maps.

The firmware can allocate ingress and egress context ids anywhere from
its configured range. Size the iq/eq maps to match the entire range
instead of assuming that the firmware always allocates the first
available context id.

Reported by: Baptiste Wicht @ Verisign
MFC after: 1 week
Sponsored by: Chelsio Communications