ASoC: wcd9335: Update zdet gpio control based on current status

It is possible that Z-det gpio is already in the requested
state when impedance detection requests for "high". In that
case, return non-zero value so that the gpio status will not
changed at the end of impedance detection.

Change-Id: If7b14100e40054e77f2071051706a737bd27f5c5
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>