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/Kconfig b/drivers/sound/Kconfig
index 4b893f0..c1847df 100644
--- a/drivers/sound/Kconfig
+++ b/drivers/sound/Kconfig
@@ -40,6 +40,18 @@
 	  option provides an implementation for sound_init() and
 	  sound_play().
 
+config SOUND_I8254
+	bool "Intel i8254 timer / beeper"
+	depends on SOUND
+	help
+	  This enables support for a beeper that uses the i8254 timer chip.
+	  This can emit beeps at a fixed frequency. It is possible to control
+	  the length of the beeps, by turning a beep on, waiting for a period
+	  of time, then turning it off.
+
+	  This is quite an old feature, called PIT (Programmable Interval
+	  Timer), but is nonetheless still available on modern x86 machines.
+
 config SOUND_INTEL_HDA
 	bool "Intel HDA audio codec"
 	depends on SOUND