ALSA: bcd2000: Fix a UAF bug on the error path of probing
In the Linux kernel, the following vulnerability has been resolved:

ALSA: bcd2000: Fix a UAF bug on the error path of probing

When the driver fails in snd_card_register() at probe time, it will free
the 'bcd2k->midi_out_urb' before killing it, which may cause a UAF bug.

The following log can reveal it:

[   50.727020] BUG: KASAN: use-after-free in bcd2000_input_complete+0x1f1/0x2e0 [snd_bcd2000]
[   50.727623] Read of size 8 at addr ffff88810fab0e88 by task swapper/4/0
[   50.729530] Call Trace:
[   50.732899]  bcd2000_input_complete+0x1f1/0x2e0 [snd_bcd2000]

Fix this by adding usb_kill_urb() before usb_free_urb().