ARM: stm32: Hog GPIO PF7 high on DHCOM to unlock SPI NOR nWP

The SPI NOR nWP line is connected to GPIO PF7 on the SoM,
pull the GPIO line high by default to clear SPI NOR WP.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>