sparc: Pass correct argument to lower_alloc.

ir/be/sparc/bearch_sparc.c

@@ -436,7 +436,7 @@ static void sparc_lower_for_target(void)
 		ir_graph *irg = get_irp_irg(i);
 		ir_lower_mode_b(irg, mode_Iu);
 		lower_switch(irg, 4, 256, false);
-		lower_alloc(irg, SPARC_STACK_ALIGNMENT, false, -SPARC_MIN_STACKSIZE);
+		lower_alloc(irg, SPARC_STACK_ALIGNMENT, false, SPARC_MIN_STACKSIZE);
 	}
 }