drm/meson: dw-hdmi: Fix devm_regulator_*get_enable*() conversion again

devm_regulator_get_enable_optional() returns -ENODEV if requested
optional regulator is not present. Adjust code for that, because in the
67d0a301 I've incorrectly assumed that it also returns 0 when
regulator is not present.

Reported-by: Ricardo Cañuelo <ricardo.canuelo@collabora.com>
Fixes: 67d0a301 ("drm/meson: dw-hdmi: Fix devm_regulator_*get_enable*() conversion")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230309152446.104913-1-m.szyprowski@samsung.com