Clarify the expected usage of I2C 7-bit slave addresses on ioctl(2)
interface.

While here add the cross reference to iic(4) on iicbus(4).

CR:		D210
Suggested by:	jmg
MFC after:	1 week
Correct memset size.

Submitted by:	Sascha Wildner (swildner at dragonflybsd dot org)
Reviewed by:	Kashyap Desai <kashyap.desai avagotech.com>
MFC after:	2 weeks
Apply vendor fixes for big endian support and 20GBps/25GBps link speeds.

Many thanks to Emulex for their continued support of FreeBSD!

Submitted by:	Venkata Duvvuru <VenkatKumar.Duvvuru Emulex.Com>
MFC after:	3 days