kni: fix build with kernel 3.19

kni: fix build with kernel 3.19

Due to API changes in functions ndo_dflt_bridge_getlink
(commit 2c3c031c) and ndo_fdb_add (commit f6f6424b)
in kernel 3.19, DPDK would not build.

This patch solves the problem, by checking the kernel version
and adding the necessary new parameters.

Mind that function igb_ndo_fdb_add does not need the extra parameter
if USE_CONST_DEV_UC_CHAR is not set, since that macro is only defined
when kernel is greater or equal than 3.7

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>