doc: fix typo in prog guide
doc: fix typo in prog guide

Fix trivial typo (an -> and) in description of service core masks.

Signed-off-by: Roy Franz <a58e234ead0397b00b518065b0b5eff3dd8aab1a@cavium.com>
Acked-by: John McNamara <af31595c36a4239b9676e9b3a777d3e2f15a6c4d@intel.com>

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