Staging: iio: adc: Fix warning prefer kmalloc_array over kmalloc

This patch fixes the checkpatch warning:
WARNING: Prefer kmalloc_array over kmalloc with multiply

kmalloc_array is preffered for allocating for arrays.
Signed-off-by: NDarshana Padmadas <darshanapadmadas@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/iio/adc/mxs-lradc.c

@@ -1280,7 +1280,7 @@ static int mxs_lradc_buffer_preenable(struct iio_dev *iio)
 	if (!ret)
 		return -EBUSY;
 
-	lradc->buffer = kmalloc(len * sizeof(*lradc->buffer), GFP_KERNEL);
+	lradc->buffer = kmalloc_array(len, sizeof(*lradc->buffer), GFP_KERNEL);
 	if (!lradc->buffer) {
 		ret = -ENOMEM;
 		goto err_mem;