x86_64: Correct fix for cmp-long

We cannot rely on the sign of the sub instruction because
LONG_MAX - LONG_MIN = -1 and the sign will indicate that
LONG_MAX < KONG_MIN and it is incorrect.

The fix also contains small improvement for load wide constant.

Change-Id: I74df70d7c198cebff5cad8c1d5614c1d29b79a1b
Signed-off-by: Serguei Katkov <serguei.i.katkov@intel.com>
4 files changed