libpayload: usb: Unify USB speed between XHCI stack and USB core

This patch removes the confusing concept of a special "xhci_speed" with
a different numeric value from the usual speed used throughout the USB
core (except for the places directly interacting with the xHC, which are
explicitly marked). It also moves the MPS0 decoding function into the
core and moves some definitions around in preparation of later changes
that will make the stack SuperSpeed-ready. It makes both set_address
implementations share a constant for the specification-defined
SetAddress() recovery delay and removes pointless additional delays from
the non-XHCI version.

BUG=chrome-os-partner:22139
TEST=Manual

Change-Id: I422379d05d4a502b12dae183504e5231add5466a
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/170664
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Commit-Queue: Ronald Minnich <rminnich@chromium.org>
10 files changed