Fix missing includes

Some files relied on psa_util.h to provide the includes they need.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 325bb09..a16198f 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -24,6 +24,8 @@
 
 #include "mbedtls/build_info.h"
 
+#include "mbedtls/error.h"
+
 #include "mbedtls/ssl.h"
 #include "mbedtls/cipher.h"