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/synaptics.c

@@ -1454,11 +1454,6 @@ int synaptics_init_relative(struct psmouse *psmouse)
 	return __synaptics_init(psmouse, false);
 }
 
-bool synaptics_supported(void)
-{
-	return true;
-}
-
 #else /* CONFIG_MOUSE_PS2_SYNAPTICS */
 
 void __init synaptics_module_init(void)
@@ -1470,9 +1465,4 @@ int synaptics_init(struct psmouse *psmouse)
 	return -ENOSYS;
 }
 
-bool synaptics_supported(void)
-{
-	return false;
-}
-
 #endif /* CONFIG_MOUSE_PS2_SYNAPTICS */