Fix typo in sssx name, there should be three letters 's'.

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kamil Konieczny <k.konieczny@partner.samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>