ALSA: rename "PC Speaker" and "PC Beep" controls to "Beep"

To avoid confusion in control names for the standard analog PC Beep generator
using a small Internal PC Speaker, rename all related "PC Speaker" and "PC
Beep" controls to "Beep" only. This name is more universal and can be also
used on more platforms without confusion.

Introduce also "Internal Speaker" in ControlNames.txt for systems with
full-featured build-in internal speaker.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>