regulator: gpio: don't print error on EPROBE_DEFER

Don't print out an error with the driver sees EPROBE_DEFER when
attempting to get the gpio.  These errors are usually transient; the
probe will be retried later.

Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Signed-off-by: Mark Brown <broonie@kernel.org>