thunderbolt: test: Use kunit_test_suite() macro

The new implementation of kunit_test_suite() for modules no longer
conflicts with module_init, so can now be used by the thunderbolt tests.

Also update the Kconfig entry to enable the test when KUNIT_ALL_TESTS is
enabled.

This means that kunit_tool can now successfully run and parse the test
results with, for example:
	./tools/testing/kunit/kunit.py run --arch=x86_64 \
	--kconfig_add CONFIG_PCI=y --kconfig_add CONFIG_USB4=y \
	'thunderbolt'

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>