ALSA: vx_core: off by one in vx_read_status()

This code is older than git, and I haven't tested it, but if size ==
SIZE_MAX_STATUS then we would write one space past the end of the
rmh->Stat[] array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>