ALSA: usb-audio: Check available frames for the next packet size

ALSA: usb-audio: Check available frames for the next packet size

commit d215f63d49da9a8803af3e81acd6cad743686573 upstream.

This is yet more preparation for the upcoming changes.

Extend snd_usb_endpoint_next_packet_size() to check the available
frames and return -EAGAIN if the next packet size is equal or exceeds
the given size.  This will be needed for avoiding XRUN during the low
latency operation.

As of this patch, avail=0 is passed, i.e. the check is skipped and no
behavior change.

Link: https://lore.kernel.org/r/20210929080844.11583-7-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>