Follow the lead of mxgb(4) and build the module for ixgb(4).
Follow the lead of mxgb(4) and build the module for ixgb(4).

Originally it wasn't enabled since the hardware wasn't commonplace,
but as 10GE hardware is becoming more widely used, building the module
by default should be beneficial.

Approved by:	rwatson (mentor)
MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase