regulator: core: Correct default return value for full constraints

Once we have full constraints then all supply mappings should be known to
the regulator API. This means that we should treat failed lookups as fatal
rather than deferring in the hope of further registrations but this was
broken by commit 9b92da1f "regulator: core: Fix default return
value for _get()" which was targeted at DT systems but unintentionally
broke non-DT systems by changing the default return value.

Fix this by explicitly returning -EPROBE_DEFER from the DT lookup if we
find a property but no corresponding regulator and by having the non-DT
case default to -ENODEV when we have full constraints.

Fixes: 9b92da1f

 "regulator: core: Fix default return value for _get()"
Signed-off-by: Mark Brown <broonie@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org