i2c: stm32f7: support i2c_*_dma_safe_msg_buf APIs

`i2c_*_dma_safe_msg_buf` APIs operate on a `struct i2c_msg`.
The get operation make sure the I2C buffer is DMA'able according to its
buffer length, or if the memory use is DMA coherent for example and
return a valid pointer for safe DMA access to be used.
The put operation release the pointer.
Prefer using generic API's than relying on private tests.

Acked-by: Alain Volmat <alain.volmat@foss.st.com>
Signed-off-by: Clément Le Goffic <clement.legoffic@foss.st.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20250704-i2c-upstream-v4-3-84a095a2c728@foss.st.com