dt-bindings: ti-serdes-mux: Add defines for J784S4 SoC

There are 4 lanes in the single instance of J784S4 SERDES. Each SERDES
lane mux can select up to 4 different IPs. Define all the possible
functions.

Signed-off-by: Matt Ranostay <mranostay@ti.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/755a14f1-92ad-ce4b-3fde-2a4b0650475c@axentia.se
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>