kunit: fix Kconfig for build-in tests USB4 and Nitro Enclaves

Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
if KUNIT is compiled as a module. This leads to issues if KUNIT is being
packaged separately from the core kernel and when KUNIT is run baremetal
without the required driver compiled into the kernel.

Fixes: 635dcd16 ("thunderbolt: test: Use kunit_test_suite() macro")
Fixes: fe5be808 ("nitro_enclaves: test: Use kunit_test_suite() macro")
Signed-off-by: Nico Pache <npache@redhat.com>
Reviewed-by: David Gow <davidgow@google.com>
Reviewed-by: Andra Paraschiv <andraprs@amazon.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>