GBE: fix one potential bug in UnsignedI64ToFloat.
GBE: fix one potential bug in UnsignedI64ToFloat.

Set exp to a proper value to make sure all the inactive lanes
flag bits are 1s which satisfy the requirement of the following
ALL16/ALL8H condition check.

v2:
enable the first JMPI's optimization rather the second,
as it has higher probability.

Signed-off-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@intel.com>
Reviewed-by: "Yang, Rong R" <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>

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