pinctrl: pinctrl_stm32: Add slew rate support for stm32_pinctrl_get_pin_muxing()

For debug purpose, it should be useful to indicate the slew rate for
each pins.
Add ospeed register information for pins which are configured in
either alternate function or gpio output.

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