calls.c: fix warning on targets without REG_PARM_STACK_SPACE

gcc/ChangeLog:
	* calls.c (can_implement_as_sibling_call_p): Mark param
	reg_parm_stack_space with ATTRIBUTE_UNUSED.

From-SVN: r236527

gcc/ChangeLog

+2016-05-20  David Malcolm  <dmalcolm@redhat.com>
+
+	* calls.c (can_implement_as_sibling_call_p): Mark param
+	reg_parm_stack_space with ATTRIBUTE_UNUSED.
+
 2016-05-20  Uros Bizjak  <ubizjak@gmail.com>
 
 	* gcc/config/i386/i386.c (ix86_rtx_costs) <case CONST_DOUBLE>:

gcc/calls.c

@@ -2373,7 +2373,7 @@ static bool
 can_implement_as_sibling_call_p (tree exp,
 				 rtx structure_value_addr,
 				 tree funtype,
-				 int reg_parm_stack_space,
+				 int reg_parm_stack_space ATTRIBUTE_UNUSED,
 				 tree fndecl,
 				 int flags,
 				 tree addr,