ALSA: ALS4000, slight mixer improvements

- add 8kHz / 20 kHz low-pass filter switch control
- add ALS4000 Mono capture route control
- add annotations to specs pages
- improve ALS4000 PM saved regs selection (remove SB dummy register,
  add missing ones)
- add some missing ALS4000 register defines
- constify two variables

Signed-off-by: Andreas Mohr <andi@lisas.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/sb.h b/include/sound/sb.h
index 85f93c5..4e62ee1 100644
--- a/include/sound/sb.h
+++ b/include/sound/sb.h
@@ -249,6 +249,7 @@
 #define SB_ALS4000_3D_AUTO_MUTE	0x52
 #define SB_ALS4000_ANALOG_BLOCK_CTRL 0x53
 #define SB_ALS4000_3D_DELAYLINE_PATTERN 0x54
+#define SB_ALS4000_CR3_CONFIGURATION	0xc3 /* bit 7 is Digital Loop Enable */
 #define SB_ALS4000_QSOUND	0xdb
 
 /* IRQ setting bitmap */
@@ -330,7 +331,8 @@
 	SB_MIX_DOUBLE,
 	SB_MIX_INPUT_SW,
 	SB_MIX_CAPTURE_PRO,
-	SB_MIX_CAPTURE_DT019X
+	SB_MIX_CAPTURE_DT019X,
+	SB_MIX_MONO_CAPTURE_ALS4K
 };
 
 #define SB_MIXVAL_DOUBLE(left_reg, right_reg, left_shift, right_shift, mask) \