examples/performance-thread: fix size of destination port ids

examples/performance-thread: fix size of destination port ids

After extending IPv4 next hop in lpm library, size of dst_port array was
changed from 16 to 32 bits in l3fwd-thread example, without modification
of the rest of path written for 16 bit value.

This patch uses similar approach for fix, like in commit 8353a36a9b4b
("examples/l3fwd: fix size of destination port ids"), restoring 16 bit size
for destination port ids and doing necessary conversion from 32 to 16 bit
after lpm_lookupx4.

Fixes: dc81ebbacaeb ("lpm: extend IPv4 next hop field")

Signed-off-by: Tomasz Kulasek <tomaszx.kulasek@intel.com>