This fixes warnings like the following during bootstrap:

sparc-sun-solaris2.11/libstdc++-v3/include/bits/atomic_futex.h:324:53: warning: unused parameter ‘__mo’ [-Wunused-parameter]
  324 |     _M_load_when_equal(unsigned __val, memory_order __mo)
      |                                        ~~~~~~~~~~~~~^~~~

libstdc++-v3/ChangeLog:

	* include/bits/atomic_futex.h (__atomic_futex_unsigned): Remove
	names of unused parameters in non-futex implementation.