ALSA: snd_usb_audio: fix SB Extigy IR Remote regression

ALSA: snd_usb_audio: fix SB Extigy IR Remote regression

The support for the SB Extigy's remote seems to be broken in all
recent ALSA versions, including 1.0.17. The driver detects the event
correctly, then submits a URB to query the RC code. On the Extigy, the
URB is submitted with a length of 2 bytes. My hardware, however, only
replies with 1 byte, containing the correct RC button code. The
current implementation discards this as being too short. (line 1784 of
usbmixer.c)

This patch specifies a "minimum packet length" in the remote control
configuration. I've left the values for the Audigy 2/Live! the same as
the packet length, as I'm assuming the existing code works with them.
(I don't have the hardware to confirm) This fixes the Extigy RC
support, e.g. for use with Lirc.

Signed-off-by: Phillip Michael Jordan <phil@philjordan.eu>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>