ALSA: firewire-lib: replace in_interrupt() with in_softirq()

Tasklet is used to handle isochronous context of 1394 OHCI. The explicit
usage of in_softirq() may be preferable than in_interrupt().

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210611083425.61204-1-o-takashi@sakamocchi.jp


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