arm64: dts: ti: k3-am65: Add simple-mfd compatible to SerDes control nodes

arm64: dts: ti: k3-am65: Add simple-mfd compatible to SerDes control nodes

The SerDes control nodes contain both a clock and clock mux, this is
a simple MFD. Add this to the compatible string list.

Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Closes: https://lore.kernel.org/linux-arm-kernel/cover.1723653439.git.jan.kiszka@siemens.com/
Fixes: da795dc4f2a0 ("arm64: dts: ti: k3-am65: Move SerDes mux nodes under the control node")
Signed-off-by: Andrew Davis <afd@ti.com>
Tested-by: Jan Kiszka <jan.kiszka@siemens.com>
Link: https://lore.kernel.org/r/20240821162337.33774-2-afd@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>