Even if a gpio pin is set to output, we still need to set INPUT_EN
functionality (by clearing INPUT_EN bit) to be able to read the pin's
level.

E.g. without this change, we'll always read low level state from sysfs.

Cc: <stable@vger.kernel.org> # v3.14+
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>