Input: psmouse - use IS_ENABLED instead of homegrown code

Instead of having various protocols provide <protocol>_supported()
functions, let's use IS_ENABLED() macro that works well in "if" statements.

Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/focaltech.c

@@ -424,11 +424,6 @@ fail:
 	return error;
 }
 
-bool focaltech_supported(void)
-{
-	return true;
-}
-
 #else /* CONFIG_MOUSE_PS2_FOCALTECH */
 
 int focaltech_init(struct psmouse *psmouse)
@@ -438,9 +433,4 @@ int focaltech_init(struct psmouse *psmouse)
 	return 0;
 }
 
-bool focaltech_supported(void)
-{
-	return false;
-}
-
 #endif /* CONFIG_MOUSE_PS2_FOCALTECH */