fizz: usb_mux: Split struct usb_mux in fizz board
fizz: usb_mux: Split struct usb_mux in fizz board

Update fizz board to use new struct usb_mux_chain.

BUG=b:236274003
TEST=make buildall
BRANCH=None

Cq-Depend: chromium:3748785
Signed-off-by: Tomasz Michalec <a547db31280d14f095c760a23a7523d0b1e55fe6@semihalf.com>
Change-Id: I4c250392a1f944d0bae6d8b897d1d5818fe037e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3779636
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Commit-Queue: Tomasz Michalec <c064a6042954d4ba0805003dc021b76413ff1548@google.com>
Tested-by: Tomasz Michalec <c064a6042954d4ba0805003dc021b76413ff1548@google.com>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec