selftests/tls: fix TLS tests with CONFIG_TLS=n

Build bot reports some recent TLS tests are failing
with CONFIG_TLS=n. Correct the expected return code
and skip TLS installation if not supported.

Tested with CONFIG_TLS=n and CONFIG_TLS=m.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Fixes: cf32526c ("selftests/tls: add a test for ULP but no keys")
Fixes: 65d41fb3 ("selftests/tls: add a bidirectional test")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>