app/regex: fix crash in options parsing

app/regex: fix crash in options parsing

getopt_long() parses command-line arguments. One of its arguments
'longopts' is a pointer to the first element of an array of struct
option.  The last element of the array has to be filled with zeros
to mark the end of options. For example:

struct option longopts[] = {
{ "help",  0, 0, ARG_HELP},
....
/* End of options */
{ 0, 0, 0, 0 }
};

This commit adds the last element. Prior to this commit getopt_long()
continued parsing beyond the longopts[] array which occasionally caused
segmentation faults.

Fixes: de06137cb295 ("app/regex: add RegEx test application")
Cc: stable@dpdk.org
Signed-off-by: Ophir Munk <ophirmu@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>
Acked-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>