pinctrl: include machine header to core.h

struct pinctrl_setting contains an enum pinctrl_map_type
field, so we need to include machine.h. Also fix kerneldoc
to indicate that the pinctrl_setting is about both muxing
and other config.

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