GBE: fix legacy read64 mix pointer bug.
GBE: fix legacy read64 mix pointer bug.

Tmp register is start from insn.extra.elem.

Signed-off-by: Yang Rong <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>

wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet,wdv4758h/beignet