usb_mux: Correct an error print.
usb_mux: Correct an error print.

BUG=none
BRANCH=none
TEST=none

Change-Id: Ica208bf8d6f34c856073b06633560de08792976c
Signed-off-by: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/368590
Reviewed-by: Martin Roth <79230511ccf79da3f7e9e82dbcc9c1ec2f734fa0@chromium.org>
Reviewed-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>

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