Depthcharge's current cros_ec code doesn't really match the
object-oriented one-instance-per-device design of its other drivers.
Instead, it is a singleton design with hardcoded support for only up to
one additional chip by passing devidx=1 to certain functions. In
addition, the vboot callback implementations for EC software sync are
tightly interwoven with the cros_ec driver.

This patch changes that code to be more in line with depthcharge's other
drivers. EC and PD chips are represented as separate objects (sharing
the same bus object), and the connection to vboot callbacks is
abstracted in a VbootEcOps superclass. This is intended to make it
easier to hook up other embedded controllers that don't run the Chrome
EC embedded OS to vboot's software sync mechanism, such as the ANX7688
used on Elm. (This is intended to be the first step. We may or may not
decide that it makes sense to also make changes to vboot code and the
callback interface later.)

Also try to clean up namespacing a bit (cros_ec_... only for exported
functions), only export functions that are really needed by other files,
and remove some unused code.

BUG=chrome-os-partner:52434
TEST=FAFT on Oak. Manually triggered software sync both after cold
reboot and when the EC was already in RW.

Change-Id: I6666c4382ef40d1211995101c97a52346963fa4a
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/341542


Reviewed-by: Aaron Durbin <adurbin@chromium.org>