ASoC: cs35l33: Fix testing return value of devm_gpiod_get_optional

devm_gpiod_get_optional() returns NULL when the gpio is not assigned.
So the if (PTR_ERR(cs35l33->reset_gpio) == -ENOENT) test is always false.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Paul Handrigan <Paul.Handrigan@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>