gpio: of: don't warn if ignored GPIO flag matches the behavior

Some devicetrees specify the ACTIVE_LOW flag in the fixed regulator GPIO
handle. While this has always been ignored, it's consistent with the
behavior of the regulator binding in the absence of the
"enable-active-high" DT property. It doesn't make much sense to print a
user visible warning for a configuration which is consistent, so only
print the warning if the GPIO flag contradicts the behavior dictated by
by the enable-active-high property.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
[Bartosz: coding style tweak]
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>