gpio: stm32: correct the bias management

Use the bias configuration for all the GPIO configurations and not
only for input GPIO, as indicated in Reference manual
(Table 81. Port bit configuration table).

Fixes: 43efbb6a ("gpio: stm32: add ops get_dir_flags")
Fixes: f13ff88b ("gpio: stm32: add ops set_dir_flags")
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>