glsl: Remove ir_call::get_callee() and set_callee().

Previously, set_callee() performed some assertions about the type of the
ir_call; protecting the bare pointer ensured these checks would be run.

However, ir_call no longer has a type, so the getter and setter methods
don't actually do anything useful.  Remove them in favor of accessing
callee directly, as is done with most other fields in our IR.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/ir_clone.cpp

@@ -398,9 +398,9 @@ public:
        * table.  If it is found, replace it with the value from the table.
        */
       ir_function_signature *sig =
-	 (ir_function_signature *) hash_table_find(this->ht, ir->get_callee());
+	 (ir_function_signature *) hash_table_find(this->ht, ir->callee);
       if (sig != NULL)
-	 ir->set_callee(sig);
+	 ir->callee = sig;
 
       /* Since this may be used before function call parameters are flattened,
        * the children also need to be processed.