pcap: fix build error introduced by kvargs

pcap: fix build error introduced by kvargs

Due to a merge conflict between commits 4c745617a1 and 9d5752d80,
rte_eth_pcap.c was not compiling with the following error:

rte_eth_pcap.c: In function 'rte_pmd_init_internals':
rte_eth_pcap.c:559:30: error: dereferencing pointer to incomplete type
rte_eth_pcap.c:560:15: error: dereferencing pointer to incomplete type
rte_eth_pcap.c:561:18: error: dereferencing pointer to incomplete type
rte_eth_pcap.c:603:47: error: dereferencing pointer to incomplete type
rte_eth_pcap.c: In function 'rte_pmd_pcap_init':
rte_eth_pcap.c:732:73: error: 'dict' undeclared (first use in this
  function)
rte_eth_pcap.c:732:73: note: each undeclared identifier is reported
  only once for each function it appears in

This commit replaces "struct args_dict" by "struct rte_kvargs" to fix
the compilation issue.

By the way, it also removes the declaration of these functions from
the header file as no other file in DPDK references one of them. It
avoids to include <rte_kvargs.h> in rte_eth_pcap.h.

Reported-by: Meir Tseitlin <mirots@gmail.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>