pipeline: introduce SWX cksub instruction
pipeline: introduce SWX cksub instruction

The cksub (i.e. checksum subtract) instruction is used to update the
1's complement sum commonly used by protocols such as IPv4, TCP or
UDP.

Signed-off-by: Cristian Dumitrescu <25468b8a3698eeb3c368247f8635924bb4a1ce2c@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk