tests/gem_reset_stats: end hanging batch properly

tests/gem_reset_stats: end hanging batch properly

As we use chained batch into itself to hang the gpu, there
was no need to end the batchbuffer with BATCH_BUFFER_END.

With the introduction of command parser, the batch
need to have proper BATCH_BUFFER_END in it or it
will be rejected.

While at it, shift the upper half of batch gtt_offset
accordingly with gen8+

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>