pinctrl: single: Prepare for supporting SoC specific features

Let's replace is_pinconf with flags and add struct pcs_soc_data
so we can support SoC specific features like pin wake-up events.

Done in collaboration with Roger Quadros <rogerq@ti.com>.

Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Prakash Manjunathappa <prakash.pm@ti.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>