regulator: wm8994: Don't use devres for enable GPIOs

The regulator core takes over managing the lifetime of the enable GPIO
once the regulator is registered. As such we shouldn't register the
enable GPIO using devm, or it will be freed twice.

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>