GBE: Change 64bit integer storage in register

GBE: Change 64bit integer storage in register

Previously, we store low/high half of 64bit together, which need several
32bit instructions to do one 64bit instruction. Now we simply change its
storage in register, low 32bit of all lanes are stored together, and then the
high 32bit of all lanes. This will make long support cleaner and less
32bit instructions needed.

v2:
fix a typo when getRegAtrrib().
Refine SelectionVector alignment.

Signed-off-by: Ruiling Song <ruiling.song@intel.com>
Reviewed-by: "Yang, Rong R" <rong.r.yang@intel.com>