Give a better name for struct member

Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
diff --git a/include/psa/crypto_builtin_primitives.h b/include/psa/crypto_builtin_primitives.h
index 260619c..31f4aa6 100644
--- a/include/psa/crypto_builtin_primitives.h
+++ b/include/psa/crypto_builtin_primitives.h
@@ -105,7 +105,7 @@
     uint8_t MBEDTLS_PRIVATE(iv_length);
     uint8_t MBEDTLS_PRIVATE(block_length);
     union {
-        unsigned int MBEDTLS_PRIVATE(initialised);
+        unsigned int MBEDTLS_PRIVATE(dummy);
         mbedtls_cipher_context_t MBEDTLS_PRIVATE(cipher);
     } MBEDTLS_PRIVATE(ctx);
 } mbedtls_psa_cipher_operation_t;