arm64: dts: ti: j721e-main: Fix 'dtbs_check' in serdes_ln_ctrl node

Fix 'dtbs_check' in serdes_ln_ctrl (mux@4080) node by changing the node
name to mux-controller@4080.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20211126084555.17797-3-kishon@ti.com