net/iavf: fix vector Rx

net/iavf: fix vector Rx

The limitation of burst size in vector rx was removed, since it should
retrieve as much received packets as possible. And also the scattered
receive path should use a wrapper function to achieve the goal of
burst maximizing.

Bugzilla ID: 516
Fixes: 319c421f3890 ("net/avf: enable SSE Rx Tx")
Fixes: 1162f5a0ef31 ("net/iavf: support flexible Rx descriptor in SSE path")
Fixes: 5b6e8859081d ("net/iavf: support flexible Rx descriptor in AVX path")
Cc: stable@dpdk.org
Signed-off-by: Jeff Guo <jia.guo@intel.com>
Acked-by: Morten Brørup <mb@smartsharesystems.com>
Tested-by: Wei Ling <weix.ling@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>