pinctrl: stm32: Remove dependency with DT bindings header files

Some macros where defined in DT bindings headers, whereas only used
in the driver.

This patch moves these macros to the driver side.

Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>