app/test-crypto-perf: fix compilation with -Og

app/test-crypto-perf: fix compilation with -Og

The compilation with gcc-6.3.0 and EXTRA_CFLAGS=-Og gives the following
error:

  CC cperf_test_verify.o
cperf_test_verify.c: In function ‘cperf_verify_op’:
cperf_test_verify.c:382:5: error: ‘auth’ may be used uninitialized
                           in this function
                           [-Werror=maybe-uninitialized]
  if (auth == 1) {
     ^
cperf_test_verify.c:371:5: error: ‘cipher’ may be used uninitialized
                           in this function
			   [-Werror=maybe-uninitialized]
  if (cipher == 1) {
     ^
cperf_test_verify.c:384:11: error: ‘auth_offset’ may be used
			    uninitialized in this function
			    [-Werror=maybe-uninitialized]
    res += memcmp(data + auth_offset,
           ^~~~~~~~~~~~~~~~~~~~~~~~~~
      vector->digest.data,
      ~~~~~~~~~~~~~~~~~~~~
      options->digest_sz);
      ~~~~~~~~~~~~~~~~~~~
cperf_test_verify.c:377:11: error: ‘cipher_offset’ may be used
                            uninitialized in this function
                            [-Werror=maybe-uninitialized]
    res += memcmp(data + cipher_offset,
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      vector->plaintext.data,
      ~~~~~~~~~~~~~~~~~~~~~~~
      options->test_buffer_size);
      ~~~~~~~~~~~~~~~~~~~~~~~~~~

There is no default case in the switch statement, so if options->op_type
is an unknown value, the function will use uninitialized values. Fix it
by adding a default.

Fixes: f8be1786b1b8 ("app/crypto-perf: introduce performance test application")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>