psa: free RNG implementation before checking for remaining open key slots

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index ef29b77..8005dcb 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -194,6 +194,15 @@
 /**@}*/
 
 /**
+ * \brief PSA random deinitialization.
+ *
+ * This function frees the RNG implementation used by PSA.
+ *
+ * This is an Mbed TLS extension.
+ */
+void mbedtls_psa_random_free(void);
+
+/**
  * \brief Library deinitialization.
  *
  * This function clears all data associated with the PSA layer,