tests: Get rid of mbedtls_test_unhexify() in unit test code

In test functions calling mbedtls_test_unhexify(), change the
type of the associated parameters from `char*` to `data_t`.

That way the `unhexify` operation is done by the test
framework and not by the unit test code.

Use for the new parameters of type data_t the name of the
local variable that used to store the `unhexify` version of
the `char*` parameter.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index 1f0a655..3374a07 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -313,52 +313,39 @@
 /* END_CASE */
 
 /* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_OFB */
-void aes_encrypt_ofb( int fragment_size, char *hex_key_string,
-                      char *hex_iv_string, char *hex_src_string,
-                      char *hex_expected_output_string )
+void aes_encrypt_ofb( int fragment_size, data_t *key_str,
+                      data_t *iv_str, data_t *src_str,
+                      char *expected_output_string)
 {
-    unsigned char key_str[32];
-    unsigned char iv_str[16];
-    unsigned char src_str[64];
     unsigned char output[32];
     unsigned char output_string[65];
     mbedtls_aes_context ctx;
     size_t iv_offset = 0;
     int in_buffer_len;
     unsigned char* src_str_next;
-    int key_len;
 
-    memset( key_str, 0x00, sizeof( key_str ) );
-    memset( iv_str, 0x00, sizeof( iv_str ) );
-    memset( src_str, 0x00, sizeof( src_str ) );
     memset( output, 0x00, sizeof( output ) );
     memset( output_string, 0x00, sizeof( output_string ) );
     mbedtls_aes_init( &ctx );
 
     TEST_ASSERT( (size_t)fragment_size < sizeof( output ) );
-    TEST_ASSERT( strlen( hex_key_string ) <= ( 32 * 2 ) );
-    TEST_ASSERT( strlen( hex_iv_string ) <= ( 16 * 2 ) );
-    TEST_ASSERT( strlen( hex_src_string ) <= ( 64 * 2 ) );
-    TEST_ASSERT( strlen( hex_expected_output_string ) <= ( 64 * 2 ) );
 
-    key_len = mbedtls_test_unhexify( key_str, hex_key_string );
-    mbedtls_test_unhexify( iv_str, hex_iv_string );
-    in_buffer_len = mbedtls_test_unhexify( src_str, hex_src_string );
-
-    TEST_ASSERT( mbedtls_aes_setkey_enc( &ctx, key_str, key_len * 8 ) == 0 );
-    src_str_next = src_str;
+    TEST_ASSERT( mbedtls_aes_setkey_enc( &ctx, key_str->x,
+                                         key_str->len * 8 ) == 0 );
+    in_buffer_len = src_str->len;
+    src_str_next = src_str->x;
 
     while( in_buffer_len > 0 )
     {
         TEST_ASSERT( mbedtls_aes_crypt_ofb( &ctx, fragment_size, &iv_offset,
-                                            iv_str, src_str_next, output ) == 0 );
+                                            iv_str->x, src_str_next, output ) == 0 );
 
         mbedtls_test_hexify( output_string, output, fragment_size );
-        TEST_ASSERT( strncmp( (char *) output_string, hex_expected_output_string,
+        TEST_ASSERT( strncmp( (char *) output_string, expected_output_string,
                               ( 2 * fragment_size ) ) == 0 );
 
         in_buffer_len -= fragment_size;
-        hex_expected_output_string += ( fragment_size * 2 );
+        expected_output_string += ( fragment_size * 2 );
         src_str_next += fragment_size;
 
         if( in_buffer_len < fragment_size )