ALSA: usb-audio: Fix NULL dereference in create_fixed_stream_quirk()

ALSA: usb-audio: Fix NULL dereference in create_fixed_stream_quirk()

Orabug: 23331116

[ Upstream commit 0f886ca12765d20124bd06291c82951fd49a33be ]

create_fixed_stream_quirk() may cause a NULL-pointer dereference by
accessing the non-existing endpoint when a USB device with a malformed
USB descriptor is used.

This patch avoids it simply by adding a sanity check of bNumEndpoints
before the accesses.

Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=971125
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 6ed72ce6ab8b38803b12df8c62a3a52becf19017)

Signed-off-by: Dan Duval <dan.duval@oracle.com>