include: dt-bindings: Add STM32H7 pinctrl DT defines

Adds common pinctrl device tree defines for STM32H743 and
STM32H753 MCU.
Signed-off-by: NAlexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>