arm64: dts: st: add timer nodes on stm32mp251

arm64: dts: st: add timer nodes on stm32mp251

Add timers support on STM32MP25 SoC. Use dedicated compatible to handle
new features and instances introduced with this SoC. STM32MP25 SoC has
various timer flavours, each group has its own specific feature list:
- Advanced-control timers (TIM1/TIM8/TIM20)
- General-purpose timers (TIM2/TIM3/TIM4/TIM5)
- Basic timers (TIM6/TIM7)
- General-purpose timers (TIM10/TIM11/TIM12/TIM13/TIM14)
- General purpose timers (TIM15/TIM16/TIM17)

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20250110091922.980627-7-fabrice.gasnier@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>