When requesting GPIO line the probe can be deferred.
In such case don't spam logs with an error message.
This can be achieved by switching to dev_err_probe().

Fixes: 5c1d824c ("leds: lm3697: Introduce the lm3697 driver")
Cc: Dan Murphy <dmurphy@ti.com>
Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>