Adds the pca954x muxes expected.

Tested: Booted quanta-q71l image to userspace.
Signed-off-by: Patrick Venture <venture@google.com>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Message-id: 20210608202522.2677850-4-venture@google.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>