Bring in the mpr(4) driver for LSI's MPT3 12Gb SAS controllers.

This is derived from the mps(4) driver, but it supports only the 12Gb
IT and IR hardware including the SAS 3004, SAS 3008 and SAS 3108.

Some notes about this driver:
 o The 12Gb hardware can do "FastPath" I/O, and that capability is included in
   this driver.

 o WarpDrive functionality has been removed, since it isn't supported in
   the 12Gb driver interface.

 o The Scatter/Gather list handling code is significantly different between
   the 6Gb and 12Gb hardware.  The 12Gb boards support IEEE Scatter/Gather
   lists.

Thanks to LSI for developing and testing this driver for FreeBSD.

share/man/man4/mpr.4:
	mpr(4) man page.

sys/dev/mpr/*:
	mpr(4) driver files.

sys/modules/Makefile,
sys/modules/mpr/Makefile:
	Add a module Makefile for the mpr(4) driver.

sys/conf/files:
	Add the mpr(4) driver.

sys/amd64/conf/GENERIC,
sys/i386/conf/GENERIC,
sys/mips/conf/OCTEON1,
sys/sparc64/conf/GENERIC:
	Add the mpr(4) driver to all config files that currently
	have the mps(4) driver.

sys/ia64/conf/GENERIC:
	Add the mps(4) and mpr(4) drivers to the ia64 GENERIC
	config file.

sys/i386/conf/XEN:
	Exclude the mpr module from building here.

Submitted by:	Steve McConnell <Stephen.McConnell@lsi.com>
MFC after:	3 days
Tested by:	Chris Reeves <chrisr@spectralogic.com>
Sponsored by:	LSI, Spectra Logic
Relnotes:	LSI 12Gb SAS driver mpr(4) added
Add the mpr(4) man page to the man4 Makefile.

This should have been included in r265236.

Submitted by:	Steve McConnell <Stephen.McConnell@lsi.com>
MFC after:	3 days
Sponsored by:	LSI, Spectra Logic
Properly free resources in case of error.

CID:		1007032
Found with:	Coverity Prevent(tm)
MFC after:	2 weeks