Add internal implementation

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index bd20937..8874e97 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -506,10 +506,12 @@
      * any driver (i.e. none of the driver contexts are active). */
     unsigned int MBEDTLS_PRIVATE(id);
 
+    psa_driver_sign_hash_interruptible_context_t MBEDTLS_PRIVATE(ctx);
+
     size_t MBEDTLS_PRIVATE(num_ops);
 };
 
-#define PSA_SIGN_HASH_INTERRUPTIBLE_OPERATION_INIT { 0, 0 }
+#define PSA_SIGN_HASH_INTERRUPTIBLE_OPERATION_INIT { 0, { 0 }, 0 }
 
 static inline struct psa_sign_hash_interruptible_operation_s
 psa_sign_hash_interruptible_operation_init(void)
@@ -535,10 +537,12 @@
      * any driver (i.e. none of the driver contexts are active). */
     unsigned int MBEDTLS_PRIVATE(id);
 
+    psa_driver_verify_hash_interruptible_context_t MBEDTLS_PRIVATE(ctx);
+
     size_t MBEDTLS_PRIVATE(num_ops);
 };
 
-#define PSA_VERIFY_HASH_INTERRUPTIBLE_OPERATION_INIT { 0, 0 }
+#define PSA_VERIFY_HASH_INTERRUPTIBLE_OPERATION_INIT { 0, { 0 }, 0 }
 
 static inline struct psa_verify_hash_interruptible_operation_s
 psa_verify_hash_interruptible_operation_init(void)