regulator: da9055: Fix notifier mutex lock warning

The mutex for the regulator_dev must be controlled by the caller of
the regulator_notifier_call_chain(), as described in the comment
for that function.

Failure to mutex lock and unlock surrounding the notifier call results
in a kernel WARN_ON_ONCE() which will dump a backtrace for the
regulator_notifier_call_chain() when that function call is first made.
The mutex can be controlled using the regulator_lock/unlock() API.

Fixes: f6130be6 ("regulator: DA9055 regulator driver")
Suggested-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/da9055-regulator.c

@@ -487,8 +487,10 @@ static irqreturn_t da9055_ldo5_6_oc_irq(int irq, void *data)
 {
 	struct da9055_regulator *regulator = data;
 
+	regulator_lock(regulator->rdev);
 	regulator_notifier_call_chain(regulator->rdev,
 				      REGULATOR_EVENT_OVER_CURRENT, NULL);
+	regulator_unlock(regulator->rdev);
 
 	return IRQ_HANDLED;
 }