dt-bindings: ti-serdes-mux: Add defines for J7200 SoC

There are 4 lanes in each J7200 SERDES. Each SERDES lane mux can
select upto 4 different IPs. Define all the possible functions.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Peter Rosin <peda@axentia.se>
Cc: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20200930122032.23481-2-rogerq@ti.com