ALSA: usb-audio: Don't start stream for capture at prepare

ALSA: usb-audio: Don't start stream for capture at prepare

commit 83de8f83816e8e15227dac985163e3d433a2bf9d upstream.

The recent change made mistakenly the stream for capture started at
prepare stage.  Add the stream direction check to avoid it.

Fixes: 9c9a3b9da891 ("ALSA: usb-audio: Rename early_playback_start flag with lowlatency_playback")
Link: https://lore.kernel.org/r/20211119102629.7476-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>