i40e: fix out of bound read

i40e: fix out of bound read

Klocwork reports array 'src_offset' may use index 16.
In function i40e_srcoff_to_flx_pit, index j + 1 can reach I40E_FDIR_MAX_FLEX_LEN.
This patch fixes this issue to avoid array bound.

Test report: http://www.dpdk.org/ml/archives/dev/2015-March/016030.html

Fixes: d8b90c4eabe9 ("i40e: take flow director flexible payload configuration")

Signed-off-by: Jingjing Wu <jingjing.wu@intel.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>
Tested-by: Min Cao <min.cao@intel.com>