ALSA: sh: add SuperH DAC audio driver for ALSA V4

This is a port of the sound/oss/sh_dac_audio.c driver.
The driver uses an on-chip 8-bit D/A converter, which has a speaker connected
to one of its channels, found in several ancient HP machines.
For interrupts it uses a high-resolution timer (hrtimer).
Tested on SH7709 based hp6xx (HP Jornada 680/690 and HP Palmtop 620lx/660lx).

Also, since OSS Emulation works, the old OSS sound/oss/sh_dac_audio.c driver
would be obsolete soon, and it could be removed.

Signed-off-by: Rafael Ignacio Zurita <rizurita@yahoo.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/sh/Kconfig b/sound/sh/Kconfig
index aed0f90..61139f3 100644
--- a/sound/sh/Kconfig
+++ b/sound/sh/Kconfig
@@ -19,5 +19,13 @@
 	help
 	  ALSA Sound driver for the SEGA Dreamcast console.
 
+config SND_SH_DAC_AUDIO
+	tristate "SuperH DAC audio support"
+	depends on SND
+	depends on CPU_SH3 && HIGH_RES_TIMERS
+	select SND_PCM
+	help
+	  Say Y here to include support for the on-chip DAC.
+
 endif	# SND_SUPERH