Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Exar driver for X3100 10GbE Server/Storage adapters

Features: Jumbo frames (up to 9600), LRO (Large Receive Offload),
TSO (TCP segmentation offload), RTH (Receive Traffic Hash).

Submitted by: Sriram Rapuru at Exar
MFC after: 2 weeks