lynxpoint: Move USB SMI sleep code to separate USB files

Move this to the existing USB source files so they can share some
helper functions and keep the main smihandler code cleaner.

The XHCI sleep prepare code now implements the actual sleep
preparation steps from the ref code instead of the docs.

Change-Id: Ic90adbdaba947a6b53824e548c785b4fb3990ab5
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/63800
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4406
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
5 files changed