regulator: core: Check for DT every time we check full constraints

Eliminate the gap between DT becoming available and this being used to say
we have full constraints by checking directly for DT every time we check
for full constraints. This improves interoperaton with optional regulator
support.

Signed-off-by: Mark Brown <broonie@linaro.org>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 1f31492..6a75794 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -121,7 +121,7 @@
 
 static bool have_full_constraints(void)
 {
-	return has_full_constraints;
+	return has_full_constraints || of_have_populated_dt();
 }
 
 /**