Remove unused config option for IPC_CLASSES

The CONFIG_IPC_CLASSES option has been introduced in a patchset adding
Intel Thread Director support. Unfortunately, this patchset had to be
removed due to complications (see issues #1084 and #1120), which was
done in commits b6c8d6ad356 ("Update v6.2 patches") and a53f55d8f0f
("Update v6.1 patches"). Those commits accidentally left the now unused
CONFIG_IPC_CLASSES option in place, so remove it now.

configs/surface-6.1.config

@@ -61,11 +61,6 @@ CONFIG_VIDEO_OV8865=m
 ##
 CONFIG_APDS9960=m
 
-##
-## For Intel Thread Director (Alder-Lake)
-##
-CONFIG_IPC_CLASSES=y
-
 ##
 ## Other Drivers
 ##

configs/surface-6.3.config

@@ -62,11 +62,6 @@ CONFIG_VIDEO_OV8865=m
 ##
 CONFIG_APDS9960=m
 
-##
-## For Intel Thread Director (Alder-Lake)
-##
-CONFIG_IPC_CLASSES=y
-
 ##
 ## Other Drivers
 ##

configs/surface-6.4.config

@@ -62,11 +62,6 @@ CONFIG_VIDEO_OV8865=m
 ##
 CONFIG_APDS9960=m
 
-##
-## For Intel Thread Director (Alder-Lake)
-##
-CONFIG_IPC_CLASSES=y
-
 ##
 ## Other Drivers
 ##