include: dt-bindings: Add STM32H7 pinctrl DT defines

Adds common pinctrl device tree defines for STM32H743 and
STM32H753 MCU.

Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>