drm/panel: sitronix-st7789v: improve error handling

Improve error handling in the probe routine, so that probe
defer errors are captured in /sys/kernel/debug/devices_deferred

Reviewed-by: Michael Riesch <michael.riesch@wolfvision.net>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230714013756.1546769-8-sre@kernel.org