sound: usb-audio: handle wMaxPacketSize for FIXED_ENDPOINT devices

For audio devices that do not have proper audio descriptors (e.g.,
Edirol UA-20), we use hardcoded parameters from our quirks list.
However, we must still read the maximum packet size from the standard
endpoint descriptor; otherwise, we might use packets that are too big
and therefore rejected by the USB core.

Signed-off-by: Clemens Ladisch <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/usb/usbaudio.c

···
 		return -EINVAL;
 	}
 	alts = &iface->altsetting[fp->altset_idx];
+	fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
 	usb_set_interface(chip->dev, fp->iface, 0);
 	init_usb_pitch(chip->dev, fp->iface, alts, fp);
 	init_usb_sample_rate(chip->dev, fp->iface, alts, fp, fp->rate_max);