counter: stm32-timer-cnt: add support for stm32mp25

Add support for STM32MP25 SoC. There are new counter modes that may be
implemented in later. Still, use newly introduced compatible to handle
this new HW variant and avoid being blocked with existing compatible
in SoC dtsi file. Modes supported currently still remains compatible.
New timer 20 has encoder capability, add it to the list.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/20250110091922.980627-4-fabrice.gasnier@foss.st.com


Signed-off-by: William Breathitt Gray <wbg@kernel.org>