leds: ktd2692: Fix an error handling path

In 'ktd2692_parse_dt()', if an error occurs after a successful
'regulator_enable()' call, we should call 'regulator_enable()'.

This is the same in 'ktd2692_probe()', if an error occurs after a
successful 'ktd2692_parse_dt()' call.

Instead of adding 'regulator_enable()' in several places, implement a
resource managed solution and simplify the remove function accordingly.

Fixes: b7da8c5c ("leds: Add ktd2692 flash LED driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Pavel Machek <pavel@ucw.cz>