gpio: of: Restrict enable-gpio quirk to regulator-gpio

Commit 0e7d6f94 ("gpio: of: Apply regulator-gpio quirk only to
enable-gpios") breaks the device tree ABI specified in the device tree
bindings for fixed regulators (compatible "regulator-fixed"). According
to these bindings the polarity of the GPIO is exclusively controlled by
the presence or absence of the enable-active-high property. As such the
polarity quirk implemented in of_gpio_flags_quirks() must be applied to
the GPIO specified for fixed regulators.

However, commit 0e7d6f94 ("gpio: of: Apply regulator-gpio quirk only
to enable-gpios") restricted the quirk to the enable-gpios property for
fixed regulators as well, whereas according to the commit message itself
it should only apply to "regulator-gpio" compatible device tree nodes.

Fix this by actually implementing what the offending commit intended,
which is to ensure that the quirk is applied to the GPIO specified by
the "enable-gpio" property for the "regulator-gpio" bindings only.

This fixes a regression on Jetson TX1 where the fixed regulator for the
HDMI +5V pin relies on the flags quirk for the proper polarity.

Fixes: 0e7d6f94

 ("gpio: of: Apply regulator-gpio quirk only to enable-gpios")
Signed-off-by: Thierry Reding <treding@nvidia.com>
Tested-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>