backlight: pwm_bl: Use dev_err_probe

Use dev_err_probe to simplify error paths. Also let dev_err_probe handle
the -EPROBE_DEFER case and add an entry to
/sys/kernel/debug/devices_deferred when deferred.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20231117120625.2398417-1-alexander.stein@ew.tq-group.com


Signed-off-by: Lee Jones <lee@kernel.org>