These SerDes lane select muxes use bits from the same register as
the SerDes clock select mux. Make the lane select mux a child
of the SerDes control node.

This removes one more requirement on scm-conf being a syscon node
which will later be converted to fix a couple DTS check warnings.
Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20240326185627.29852-2-afd@ti.comSigned-off-by: Nishanth Menon <nm@ti.com>