flash: stm32_ospi: weak callbacks cannot be used by multiple octospi drivers

[721082]

Is your enhancement proposal related to a problem? Please describe.
On the stm32u5a9xx, if we want to use octospi1 for the zephyr/drivers/flash/flash_stm32_ospi.c and octospi2 for a display we cannot use HAL_OSPI_IRQHandler() in the octospi2 isr because some weak functions are defined in the flash driver, like HAL_OSPI_TxCpltCallback() and they would be called on octospi2 interrupts.

Describe the solution you'd like
1/ I would like to be able to call HAL_OSPI_IRQHandler() in the display driver isr because it contains a bit of logic. To do so, I think it should be possible in stm32cube hal to use callbacks instead of weak functions but it requires to enable it directly in stm32u5xx_hal_conf.h as it's not configurable using Kconfig.

Describe alternatives you've considered
2/ An alternative would be to copy paste the HAL_OSPI_IRQHandler() function into the display driver.
3/ A second alternative would be to implement a octospi driver for st,stm32-ospi and move into it the octospi related part from the flash and display drivers. Then in this driver we should be able to define the weak callbacks.

Additional context

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[erwango]

Using callbacks should indeed be the way to go.
However, it is preferable to void modifying directly stm32u5xx_hal_conf.h and ideally solution should be the most generic possible to easily scale through series and drivers (if it happen that callback could be useful in other cases).
What about using #undef / #define in a dedicated file and controlled by new dedicated Kconfig symbols ?