ALSA: firewire-motu: Correct a typo in the clock proc string

ALSA: firewire-motu: Correct a typo in the clock proc string

BugLink: https://bugs.launchpad.net/bugs/1860125
commit 0929249e3be3bb82ee6cfec0025f4dde952210b3 upstream.

Just fix a typo of "S/PDIF" in the clock name string.

Fixes: 4638ec6ede08 ("ALSA: firewire-motu: add proc node to show current statuc of clock and packet formats")
Acked-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191030100921.3826-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>