drm/bridge: anx7625: fix not correct return value

At some time, the original code may return non zero value, force return 0
if operation finished.

Reviewed-by: Robert Foss <robert.foss@linaro.org>
Signed-off-by: Xin Ji <xji@analogixsemi.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20211104033609.2634452-1-xji@analogixsemi.com