[Midnightbsd-cvs] src: initcpu.c: Add workaround for errata #721 on AMD CPUs.

[laffer1 at midnightbsd.org]

Log Message:
-----------
Add workaround for errata #721 on AMD CPUs.

http://support.amd.com/us/Processor_TechDocs/41322_10h_Rev_Gd.pdf

test case from dragonfly: http://leaf.dragonflybsd.org/mailarchive/kernel/2012-03/msg00040.html

Obtained from: DragonFly

Modified Files:
--------------
    src/sys/amd64/amd64:
        initcpu.c (r1.6 -> r1.7)
        (http://cvsweb.midnightbsd.org/src/sys/amd64/amd64/initcpu.c?r1=1.6&r2=1.7)