ALSA: usb-audio: Remove unneeded wmb() in mixer_quirks

ALSA: usb-audio: Remove unneeded wmb() in mixer_quirks

Adding a memory barrier before wake_up() in
snd_usb_soundblaster_remote_complete() is supposed to ensure the write
to mixer->rc_code is visible in wait_event_interruptible() from
snd_usb_sbrc_hwdep_read().

However, this is not really necessary, since wake_up() is just a wrapper
over __wake_up() which already executes a full memory barrier before
accessing the state of the task to be waken up.

Drop the redundant call to wmb() and implicitly fix the checkpatch
complaint:

  WARNING: memory barrier without comment

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20250526-dualsense-alsa-jack-v1-8-1a821463b632@collabora.com