regulator: core: Handle probe deferral from DT when resolving supplies

When resolving regulator-regulator supplies we ignore probe deferral
returns from regulator_dev_lookup() (such as are generated for DT when
we can see a supply is registered) and just fall back to the dummy
regulator if there are full constraints (as is the case for DT).  This
means that probe deferral is broken for DT systems, fix that by paying
attention to -EPROBE_DEFER return codes like we do -ENODEV.

A further patch will simplify this further, this is a minimal fix for
the specific issue.

Fixes: 9f7e25ed (regulator: core: Handle full constraints systems when resolving supplies)
Reported-by: Sascha Hauer <s.hauer@pengutronix.de>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Mark Brown <broonnie@kernel.org>
Cc: stable@vger.kernel.org