sound: Add a driver for the i8254 beep

Add a sound driver which can output simple beeps using this legacy timer.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/sound/Makefile b/drivers/sound/Makefile
index 771c116..2a6fd74 100644
--- a/drivers/sound/Makefile
+++ b/drivers/sound/Makefile
@@ -16,4 +16,5 @@
 obj-$(CONFIG_SOUND_MAX98090)	+= max98090.o maxim_codec.o
 obj-$(CONFIG_SOUND_MAX98095)	+= max98095.o maxim_codec.o
 obj-$(CONFIG_SOUND_INTEL_HDA)	+= hda_codec.o
+obj-$(CONFIG_SOUND_I8254)	+= i8254_beep.o
 obj-$(CONFIG_SOUND_IVYBRIDGE)	+= ivybridge_sound.o