correct simd width when dst of simd_shuffle is scalar
correct simd width when dst of simd_shuffle is scalar

originally, the dst of simd_shuffle is not uniform, but if it is
optimized as scalar, just use simd_width=1 to generate sel_op/asm

Signed-off-by: Guo Yejun <1f883e24fa2949df61a83c432caa290810cece11@intel.com>
Reviewed-by: "Yang, Rong R" <78759e37dc7114caed18f74e7515c5cb519dbf6d@intel.com>

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