ALSA: scarlett2: Fix Mute/Dim/MSD Mode control names

Append "Playback Switch" to the names of "Mute" and "Dim" controls,
and append "Switch" to the "MSD Mode" control as per
Documentation/sound/designs/control-names.rst.

Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/77f1000652c37e3217fb8dad8e156bc6392abc0b.1626959758.git.g@b4.vu


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