pinctrl: st: Display pin's function when printing pinctrl debug information

pinctrl: st: Display pin's function when printing pinctrl debug information

Great for easily determining which mode a pin is operating in.
This patch was particularly helpful when debugging a recent GPIO/
Pinctrl disparity issue.

Before:
    $ cat /sys/kernel/debug/pinctrl/<pin-controller>/pinconf-pins
      pin 33 (PIO4[1]):[OE:0,PU:0,OD:0]
             [retime:0,invclk:0,clknotdat:0,de:0,rt-clk:0,rt-delay:0]

After [GPIO]:
    $ cat /sys/kernel/debug/pinctrl/<pin-controller>/pinconf-pins
      pin 33 (PIO4[1]):[OE:0,PU:0,OD:0] GPIO
             [retime:0,invclk:0,clknotdat:0,de:0,rt-clk:0,rt-delay:0]

After [Alt]:
    $ cat /sys/kernel/debug/pinctrl/<pin-controller>/pinconf-pins
      pin 33 (PIO4[1]):[OE:0,PU:0,OD:0] Alt Fn 2
             [retime:0,invclk:0,clknotdat:0,de:0,rt-clk:0,rt-delay:0]

Acked-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>