scarlet: usb_mux: Split struct usb_mux in scarlet board
scarlet: usb_mux: Split struct usb_mux in scarlet board

Update scarlet 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: I35862e08e39702c5f0287f06cabd57f16b9502e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3780406
Commit-Queue: Tomasz Michalec <c064a6042954d4ba0805003dc021b76413ff1548@google.com>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
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