examples/l3fwd: fix NEON instructions

examples/l3fwd: fix NEON instructions

To group consecutive packets with same destination port in bursts of 4
neon intrinsic data types dp1 and dp2 are calculated such that if
dst_port[]={a,b,c,d,e,f,g,h,i...} dp1 should contain: <a,b,c,d> and
dp2 should contain: <b,c,d,e> in the first iteration. dp1 should
be <e,f,g,h> and dp2 should be <f,g,h,i> in the next iteration.

Whereas the existing code incorrectly calculates dp1 as <d,e,f,g> from
second iteration.

This patch fixes the incorrect ARM NEON instructions on dp1.

Fixes: 569b290cdb36 ("examples/l3fwd: add NEON implementation")
Cc: stable@dpdk.org
Signed-off-by: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
Acked-by: Jianbo Liu <jianbo.liu@arm.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>