ALSA: caiaq: Add a sanity check for invalid EPs

As syzkaller spotted, currently caiaq driver submits a URB with the
fixed EP without checking whether it's actually available, which may
result in a kernel warning like:
  usb 1-1: BOGUS urb xfer, pipe 3 != type 1
  ------------[ cut here ]------------
  WARNING: CPU: 1 PID: 1150 at drivers/usb/core/urb.c:449
  usb_submit_urb+0xf8a/0x11d0
  Modules linked in:
  CPU: 1 PID: 1150 Comm: kworker/1:1 Not tainted
  4.14.0-rc2-42660-g24b7bd59eec0 #277
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Workqueue: usb_hub_wq hub_event
  Call Trace:
   init_card sound/usb/caiaq/device.c:467
   snd_probe+0x81c/0x1150 sound/usb/caiaq/device.c:525
   usb_probe_interface+0x35d/0x8e0 drivers/usb/core/driver.c:361
   ....

This patch adds a sanity check of validity of EPs at the device
initialization phase for avoiding the call with an invalid EP.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>