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 <[e-mail]>
Reviewed-by: Alexandru Ardelean <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/iio/industrialio-trigger.c

···
 	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

···
 
 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, ...);
+					   const char *fmt, ...);
 /**
  * iio_buffer_enabled() - helper function to test if the buffer is enabled
  * @indio_dev:		IIO device structure for device

include/linux/iio/trigger_consumer.h

···
 };
 
 
-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,