samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp_redirect

Default rlimit RLIMIT_MEMLOCK is 64KB, causes bpf map failure.
e.g.
[root@labbpf]# ./xdp_redirect $(</sys/class/net/eth2/ifindex) \
> $(</sys/class/net/eth3/ifindex)
failed to create a map: 1 Operation not permitted

The failure is seen when executing xdp_redirect while xdp_monitor
is already runnig.

Signed-off-by: Tushar Dave <tushar.n.dave@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>