iio: Add __printf() attributes to various allocation functions

A partial set of these was added to IIO a long time back.
This fills in some gaps in coverage highlighted by building
with W=1

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200913132115.800131-3-jic23@kernel.org

drivers/iio/industrialio-trigger.c

@@ -516,7 +516,8 @@ static void iio_trig_subirqunmask(struct irq_data *d)
 	trig->subirqs[d->irq - trig->subirq_base].enabled = true;
 }
 
-static struct iio_trigger *viio_trigger_alloc(const char *fmt, va_list vargs)
+static __printf(1, 0)
+struct iio_trigger *viio_trigger_alloc(const char *fmt, va_list vargs)
 {
 	struct iio_trigger *trig;
 	int i;

include/linux/iio/iio.h

@@ -691,6 +691,7 @@ static inline void *iio_priv(const struct iio_dev *indio_dev)
 
 void iio_device_free(struct iio_dev *indio_dev);
 struct iio_dev *devm_iio_device_alloc(struct device *parent, int sizeof_priv);
+__printf(2, 3)
 struct iio_trigger *devm_iio_trigger_alloc(struct device *dev,
 					   const char *fmt, ...);
 /**

include/linux/iio/trigger_consumer.h

@@ -38,7 +38,7 @@ struct iio_poll_func {
 };
 
 
-struct iio_poll_func
+__printf(5, 6) struct iio_poll_func
 *iio_alloc_pollfunc(irqreturn_t (*h)(int irq, void *p),
 		    irqreturn_t (*thread)(int irq, void *p),
 		    int type,