pinctrl: sh-pfc: Return pinconf with arguments in packed format

The pinconf-generic code expects configurations with arguments to be
returned in a packed format in order to be displayed properly by
pinconf_generic_dump_one().

Reading /sys/kernel/debug/pinctrl/e6060000.pfc/pinconf-pins on
r8a7795/salvator-x now shows:

    pin 101 (GP_3_5): output drive strength (9 mA), pin power source (3300 selector)

Instead of:

    pin 101 (GP_3_5): output drive strength (0 mA), pin power source (0 selector)

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>