The joystick (B1) on stm32mp157c-ev1 uses gpios on STMFX gpio expander.
These gpios need a pin configuration (push-pull and bias-pull-down),
described under stmfx_pinctrl node.
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>