pinctrl: stm32: Support I/O synchronization parameters

pinctrl: stm32: Support I/O synchronization parameters

Devices in the stm32mp2xx family include an I/O synchronization
block on each pin that is used to fine tune and improve the I/O
timing margins of high speed synchronous interfaces.
It can be configured to provide independently for each pin:
- skew rate on input direction or latch delay on output direction;
- inversion of clock signals or re-sampling of data signals.

Add support for the generic properties:
- skew-delay-input-ps;
- skew-delay-output-ps.

Add support for the property 'st,io-sync' to configure clock
inversion or data re-sampling mode.

Show the new parameters on debugfs pinconf-pins.

Enable it for the stm32mp257 pinctrl driver.

Co-developed-by: Valentin Caron <valentin.caron@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Co-developed-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>