cpupower: Replace a dead reference link with working ones

Replace a dead reference link to a turbo boost technology description with
a reference to a root page of the technology on the Intel site, and add
another one, describing power management technology, which includes short
description of the turbo boost.

Signed-off-by: Roman Storozhenko <romeusmeister@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>