panfrost: Properly undo pm_runtime_enable when deferring a probe

When deferring the probe because of a missing regulator, we were calling
pm_runtime_disable even if pm_runtime_enable wasn't called.

Move the call to pm_runtime_disable to the right place.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reported-by: Chen-Yu Tsai <wens@csie.org>
Cc: Robin Murphy <robin.murphy@arm.com>
Fixes: f4a3c6a4 ("drm/panfrost: Disable PM on probe failure")