drm/bridge: it6505: Fix return value check for pm_runtime_get_sync

drm/bridge: it6505: Fix return value check for pm_runtime_get_sync

`pm_runtime_get_sync` may return 1 on success. Fix the `if` statement
here to make the code less confusing, even though additional calls to
`it6505_poweron` doesn't break anything when it's already powered.

This was reported by Dan Carpenter <dan.carpenter@oracle.com> in
https://lore.kernel.org/all/Y1fMCs6VnxbDcB41@kili/

Fixes: 10517777d302 ("drm/bridge: it6505: Adapt runtime power management framework")
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221027032149.2739912-1-treapking@chromium.org