Fix alignment flag for emit_small_memory_copy

Do not unconditionally pass the "aligned" MemFlag when calling
emit_small_memory_copy.  Instead, allow the back end to rely on
the alignment info passed separately to this routine.

src/value_and_place.rs

@@ -614,7 +614,7 @@ fn transmute_value<'tcx>(
                     dst_align,
                     src_align,
                     true,
-                    MemFlags::trusted(),
+                    flags,
                 );
             }
             CValueInner::ByRef(_, Some(_)) => todo!(),