Documentation/pinctrl.txt: fix typo "with with"

Fix typo in "communicate directly with with the pinctrl subsystem".

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Landley <rob@landley.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>