dts: stm32u5: correct can1 clocks property

In #46480 the st,stm32-fdcan driver was updated to use clock_control to
configure peripheral bus clocks. However, the default clocks property
added to the can1 node of stm32u5.dtsi was not correct.

This correction has been tested on known good hardware which uses the
STM32U5 and FDCAN peripheral.

Signed-off-by: Peter Maxwell Warasila <madmaxwell@soundcomesout.com>