remove obsolete references to powertweak

This tool hasn't been maintained in over a decade, and is pretty much
useless these days.  Let's pretend it never happened.

Also remove a long-dead email address.

Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --cc Documentation/Changes
Simple merge

diff --cc drivers/pci/quirks.c
Simple merge

diff --cc fs/affs/Changes
Simple merge