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/cypress_ps2.c

@@ -710,8 +710,3 @@ err_exit:
 
 	return -1;
 }
-
-bool cypress_supported(void)
-{
-	return true;
-}