Fix zeroinitializer load/store vector assert.
Fix zeroinitializer load/store vector assert.

After move the newValueProxy of vector load/store to genWriter pass, genWriter will
get ConstantAggregateZero of load/store vector with zeroinitializer. In function processConstant,
don't handle correct type of ConstantAggregateZero, cause assert. Add the types handle.

Signed-off-by: Yang Rong <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>
Reviewed-by: "Xing, Homer" <f17cb7083eb6a94c3fb9d8f09ceefa518f721ab2@intel.com>

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