dt-bindings: net: dsa: nxp,sja1105: Add optional clock

dt-bindings: net: dsa: nxp,sja1105: Add optional clock

Add optional clock for OSC_IN and fix the below CHECK_DTBS warnings:
  arch/arm/boot/dts/nxp/imx/imx6qp-prtwd3.dtb: switch@0 (nxp,sja1105q): Unevaluated properties are not allowed ('clocks' was unexpected)

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20251010183418.2179063-1-Frank.Li@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>