ALSA: isa/wavefront: prevent out of bounds write in ioctl

The "header->number" comes from the ioctl and it needs to be clamped to
prevent out of bounds writes.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200501094011.GA960082@mwanda


Signed-off-by: Takashi Iwai <tiwai@suse.de>