MFC r309666, r310033, r310049, r310100, r310152, and r310807.

r309666:
cxgbe(4): unsigned short isn't large enough to store link speed (which
is in Mbps) for 100Gbps links.

r310033:
cxgbe(4): Retire t4_bus_space_read_8 and t4_bus_space_write_8.

r310049:
cxgbe(4): Fix the tid range shown for T6 cards in misc.tids.

r310100:
cxgbe(4): Deal with compressed error vectors.

r310152:
cxgbe(4): Fix typo in an unused macro.

r310807:
cxgbe(4): Updates to link configuration.

• Update struct link_settings and associated shared code.

• Add tunables to control FEC and autonegotiation. All ports inherit these values as their initial settings. hw.cxgbe.fec hw.cxgbe.autoneg

• Add per-port sysctls to control FEC and autonegotiation. These can be modified at any time. dev.<port>.<n>.fec dev.<port>.<n>.autoneg