topology2: gain: add mixer switch for mute control

Add a switch to gain widget for mute control. It could also be used
as MIC/SPK mute LED control purpose.

Signed-off-by: Brent Lu <brent.lu@intel.com>

tools/topology/topology2/include/components/gain.conf

@@ -152,6 +152,41 @@ Class.Widget."gain" {
 				}
 			}
 		}
+
+		# mute switch control
+		mixer."2" {
+			Object.Base.channel.1 {
+				name	"flw"
+				reg	2
+				shift	0
+			}
+			Object.Base.channel.2 {
+				name	"fl"
+				reg	2
+				shift	1
+			}
+			Object.Base.channel.3 {
+				name	"fr"
+				reg	2
+				shift	2
+			}
+			Object.Base.channel.4 {
+				name	"frw"
+				reg	2
+				shift	3
+			}
+
+			Object.Base.ops.1 {
+				name	"ctl"
+				info 	"volsw"
+				## get = 259 binds the mixer control to switch get/put handlers
+				get 	259
+				put 	259
+			}
+
+			#max 1 indicates switch type control
+			max 1
+		}
 	}
 
 	# Default attribute values for gain widget