pinctrl: stm32: Add STM32MP157 MPU support

This driver consists of 2 controllers due to a hole in mapping:
-1 controller for GPIO bankA to K.
-1 controller for GPIO bankZ.

Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>