Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Add optional support to mxge for MSI-X interrupts and multiple receive
queues (which we call slices). The NIC will steer traffic into up to
hw.mxge.max_slices different receive rings based on a configurable
hash type (hw.mxge.rss_hash_type).

Currently the driver defaults to using a single slice, so the default
behavior is unchanged. Also, transmit from non-zero slices is
disabled currently.