gpio: stm32: Rename stm32f7_gpio to stm32_gpio

As this driver is used on stm32f4/f7/h7 and stm32mp1
SoCs, rename it with a more generic name.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@st.com>