Modify the fake dst register for CMP in register allocation.
Modify the fake dst register for CMP in register allocation.

The fake dst regigster which is used to avoid the thread switch
for CMP instruction is not correct for I64 comparing.
The dst must have the same vstride as the src, so we need to
allocate a fake long type register.

Signed-off-by: Junyan He <8f73a735c668918c9613b750d3a88ebf2489599f@linux.intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

freedesktop-unofficial-mirror/beignet,zhenyw/beignet,zhenyw/beignet,zhenyw/beignet,wdv4758h/beignet,freedesktop-unofficial-mirror/beignet,wdv4758h/beignet,zhenyw/beignet,wdv4758h/beignet,wdv4758h/beignet,freedesktop-unofficial-mirror/beignet,wdv4758h/beignet,zhenyw/beignet,freedesktop-unofficial-mirror/beignet