ART: GenNegLong incorrectly handled register overlap for x86

There is a bug in the GenNegLong: it should invoke
   OpRegCopy(temp_reg, rl_result.reg.GetHigh());
instead of
   OpRegCopy(temp_reg, rl_result.reg);
But, anyway there is no need to handle the overlap
anymore because it is already handled in OpRegCopyWide()
which is invoked from StoreValueWide().
Change-Id: I379ed23434c72a91e875e753708387be6502bc57
Signed-off-by: nikolay serdjuk <nikolay.y.serdjuk@intel.com>