selftests/x86: fix spelling mistake "FAILT" -> "FAIL"

There is an spelling mistake in an a test error message. Fix it.

Acked-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>