clocksource/drivers/stm32-lptimer: Add support for stm32mp25

clocksource/drivers/stm32-lptimer: Add support for stm32mp25

On stm32mp25, DIER (former IER) must only be modified when the lptimer
is enabled. On earlier SoCs, it must be only be modified when it is
disabled. There's also a new DIEROK flag, to ensure register access
has completed.
Add a new "set_evt" routine to be used on stm32mp25, called depending
on the version register, read by the MFD core (LPTIM_VERR).

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20250429125133.1574167-4-fabrice.gasnier@foss.st.com
Signed-off-by: Lee Jones <lee@kernel.org>