ARM: dts: stm32: fix timer nodes on STM32 MCU to prevent warnings

Prevent warning seen with "make dtbs_check W=1" command:

Warning (avoid_unnecessary_addr_size): /soc/timers@40001c00: unnecessary
address-cells/size-cells without "ranges" or child "reg" property

Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>