pinctrl: single: adopt pinctrl sleep mode management

Make pinctrl-single able to handle suspend/resume events and change
hogged pins states accordingly.

Signed-off-by: Hebbar Gururaja <gururaja.hebbar@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>