This adds a callback for board specific initialization that is called
after the driver init function. This will allow a board to apply
port-specific tuning (such as USB EQ settings) to the mux chip.
BUG=chrome-os-partner:47074
BRANCH=none
TEST=build and boot on chell
Change-Id: Ib162f9a2c5239678c46b80e5517823b336f6b66c
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/313746
Reviewed-by: Shawn N <shawnn@chromium.org>