ART: Release inputs in Long.reverse intrinsic in x86

In the worst case we are using two temps each for input and output.
Then we do not have a temp left over for the swap operations. The
input is dead, however, after the first swap. So try to release it
(a no-op if it isn't actually a temp).

Bug: 22324327
Change-Id: I1fc50159afdad14160e34abeaf4670958171d6b2