staging: most: usb: sanity check channel before using it as an index into arrays

Currently channel is being sanity checked after it has been used as
an index into some arrays. Fix this by moving the sanity check of
channel before the arrays are indexed with it.

Addresses-Coverity: ("Negative array index read")
Fixes: 59ed0480 ("Staging: most: replace pr_*() functions by dev_*()")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20200507150652.52238-1-colin.king@canonical.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/usb/usb.c

@@ -664,11 +664,6 @@ static int hdm_configure_channel(struct most_interface *iface, int channel,
 	struct most_dev *mdev = to_mdev(iface);
 	struct device *dev = &mdev->usb_device->dev;
 
-	mdev->is_channel_healthy[channel] = true;
-	mdev->clear_work[channel].channel = channel;
-	mdev->clear_work[channel].mdev = mdev;
-	INIT_WORK(&mdev->clear_work[channel].ws, wq_clear_halt);
-
 	if (!conf) {
 		dev_err(dev, "Bad config pointer.\n");
 		return -EINVAL;
@@ -677,6 +672,12 @@ static int hdm_configure_channel(struct most_interface *iface, int channel,
 		dev_err(dev, "Channel ID out of range.\n");
 		return -EINVAL;
 	}
+
+	mdev->is_channel_healthy[channel] = true;
+	mdev->clear_work[channel].channel = channel;
+	mdev->clear_work[channel].mdev = mdev;
+	INIT_WORK(&mdev->clear_work[channel].ws, wq_clear_halt);
+
 	if (!conf->num_buffers || !conf->buffer_size) {
 		dev_err(dev, "Misconfig: buffer size or #buffers zero.\n");
 		return -EINVAL;