Constify cipher_wrap:mbedtls_cipher_base_lookup_table

This structure is initialized during the compilation and there is no
reason it changes.
Making it const allows the compiler to put it in .rodata section instead
of .data one.

Signed-off-by: Xavier Chapron <chapron.xavier@gmail.com>
diff --git a/library/cipher_wrap.c b/library/cipher_wrap.c
index d2fee22..b4c21ee 100644
--- a/library/cipher_wrap.c
+++ b/library/cipher_wrap.c
@@ -2425,7 +2425,7 @@
                      sizeof(mbedtls_cipher_definitions[0]))
 int mbedtls_cipher_supported[NUM_CIPHERS];
 
-const mbedtls_cipher_base_t *mbedtls_cipher_base_lookup_table[] = {
+const mbedtls_cipher_base_t * const mbedtls_cipher_base_lookup_table[] = {
 #if defined(MBEDTLS_AES_C)
     [MBEDTLS_CIPHER_BASE_INDEX_AES] = &aes_info,
 #endif