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

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

Add the 'iir' driver, for the Intel Integrated RAID controllers and
prior ICP Vortex models. This driver was developed by Achim Leubner
of Intel (previously with ICP Vortex) and Boji Kannanthanam of Intel.

Submitted by: "Kannanthanam, Boji T" <boji.t.kannanthanam@intel.com>
MFC after: 2 weeks