GBE: Disable SPF and use JMPI + IF/ENDIF to handle each blocks.

GBE: Disable SPF and use JMPI + IF/ENDIF to handle each blocks.

When enable SPF (single program flow), we always need to use f0
as the predication of almost each instruction. This bring some
trouble when we want to get tow levels mask mechanism, for an
example the SEL instruction, and some BOOL operations. We
have to use more than one instructions to do that and simply
introduce 100% of overhead of those instructions.

v2:
fix the wrong assertion.

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