Appease check-names with prefix

Adding an mbedtls_prefix is preferred to having '//no-check-names'
littered about.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/library/cipher_invasive.h b/library/cipher_invasive.h
index f158400..702f8f7 100644
--- a/library/cipher_invasive.h
+++ b/library/cipher_invasive.h
@@ -18,10 +18,9 @@
 
 #if defined(MBEDTLS_TEST_HOOKS) && defined(MBEDTLS_CIPHER_C)
 
-MBEDTLS_STATIC_TESTABLE
-int get_pkcs_padding(unsigned char *input, //no-check-names
-                     size_t input_len,
-                     size_t *data_len);
+MBEDTLS_STATIC_TESTABLE int mbedtls_get_pkcs_padding(unsigned char *input,
+                                                     size_t input_len,
+                                                     size_t *data_len);
 
 #endif