pinctrl: stm32: improve bank clocks management

pinctrl: stm32: improve bank clocks management

Instead of enabling/disabling the clock at each IO configuration update,
just keep the clock enabled from the probe.
This makes things simpler and more efficient (e.g. the time required to
toggle an output IO is drastically decreased) without significantly
increasing the power consumption.

Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Link: https://lore.kernel.org/r/20220422143608.226580-1-fabien.dessenne@foss.st.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>