pinctrl: split pincontrol states into its own header

Move the pin control state defines into its own header file,
since it is used both by machine.h which is facing the platform
and by consumer.h which is facing the drivers, and pinctrl.h
which is pinctrl-driver internal, let's not have each and every
.h file include all others, then isolation is moot.

Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>