ALSA: seq: fix passing wrong pointer in function call of compatibility layer

This commit is a fix for Linux 4.9-rc1.

In former commit, a function call of compatibility layer for ALSA sequencer
core was obsoleted by an alternative. Although, the alternative gets a
pointer to kernel stack due to mis-programming. As a result, ALSA sequencer
core unexpectedly refers over kernel stack.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 8ce8eb60 ("ALSA: seq: add an alternative way to handle ioctl requests")
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>