vppinfra: correct intrinsic called by u16x16_from_u8x16
vppinfra: correct intrinsic called by u16x16_from_u8x16

u16x16_from_u8x16() and i16x16_from_i8x16() call intrisics
_mm256_cvtepu8_epi64 and _mm256_cvtepi8_epi64. But they are not seems
doing the right data conversion from the name of the wrappers.
The correct intrinsics been called should be _mm256_cvtepu8_epi16
and _mm256_cvtepi8_epi16.

Type: fix

Change-Id: Id71de6ae1a266a370f11c33a46684202be766c43
Signed-off-by: Lijian Zhang <5bf702a4364390af4958a9b6773dbd5c19bc4226@arm.com>

FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp