kunit: Add missing newline in summary message

Add missing newline, as otherwise flushing of the final summary message
to the console log can be delayed.

Fixes: e2219db2 ("kunit: add debugfs /sys/kernel/debug/kunit/<suite>/results display")
Signed-off-by: Marco Elver <elver@google.com>
Tested-by: David Gow <davidgow@google.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>