SAI pinctrl

[yishai1999]

Added SAI pinctrl nodes
I am planning on writing an SAI I2S driver in zephyr so I need these nodes to be defined.
I'm not sure how to see if I should add more properties (pull-up, push-pull...). So LMK if I'm making some mistake.

BTW, I'm getting the following warnings when running the genpinctrl script:

Unexpected AF format: GPIO_AF2_rf (ip: STM32WL33_gpio_v1_0)                                                                                                                                                 
Skipping unsupported family STM32MP2.                                                                                                                                                                       
Skipping unsupported family STM32U3.                                                                  
Skipping unsupported family STM32WL3.

[gautierg-st]

Regex for pin generation looks good to me.
I'm not very familiar with SAI to comment on pin properties but in example project in STM32CubeIDE, there are no pull-ups, or open-drain and speed is low. So I don't think it is necessary to add anything here.