psa_crypto: add internal helper to signal that cipher driver is ready

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index d61e118..a9ba787 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -115,6 +115,14 @@
     (void) hash_alg;
     return global_data.drivers_initialized;
 }
+
+int psa_can_do_cipher(psa_algorithm_t cipher_alg)
+{
+    (void) cipher_alg;
+    return global_data.drivers_initialized;
+}
+
+
 #if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_IMPORT) ||       \
     defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY) ||     \
     defined(PSA_WANT_KEY_TYPE_DH_KEY_PAIR_GENERATE)
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 46c5775..43b1c23 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -33,6 +33,18 @@
  */
 int psa_can_do_hash(psa_algorithm_t hash_alg);
 
+/**
+ * Tell if PSA is ready for this cipher.
+ *
+ * \note            For now, only checks the state of the driver subsystem,
+ *                  not the algorithm. Might do more in the future.
+ *
+ * \param cipher_alg  The cipher algorithm (ignored for now).
+ *
+ * \return 1 if the driver subsytem is ready, 0 otherwise.
+ */
+int psa_can_do_cipher(psa_algorithm_t cipher_alg);
+
 typedef enum {
     PSA_SLOT_EMPTY = 0,
     PSA_SLOT_OCCUPIED,