crypto: rijndael: fix compilation with Clang 3.5

crypto: rijndael: fix compilation with Clang 3.5

Td0, Td1, Td2, Td3, Td4 are only used when NEED_RIJNDAEL is defined.

rijndael.c:383:18: error: unused variable 'Td0' [-Werror,-Wunused-const-variable]
static const u32 Td0[256] = {
                 ^
rijndael.c:449:18: error: unused variable 'Td1' [-Werror,-Wunused-const-variable]
static const u32 Td1[256] = {
                 ^
rijndael.c:515:18: error: unused variable 'Td2' [-Werror,-Wunused-const-variable]
static const u32 Td2[256] = {
                 ^
rijndael.c:581:18: error: unused variable 'Td3' [-Werror,-Wunused-const-variable]
static const u32 Td3[256] = {
                 ^
rijndael.c:647:18: error: unused variable 'Td4' [-Werror,-Wunused-const-variable]
static const u32 Td4[256] = {

Signed-off-by: Julien Grall <julien.grall@linaro.org>
Acked-by: Keir Fraser <keir@xen.org>