Add platform error codes

Add error codes for the platform module, to be used by
the setup \ terminate API.
diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 6b82d4f..95415dc 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -80,6 +80,7 @@
  * CHACHA20  3                  0x0051-0x0055
  * POLY1305  3                  0x0057-0x005B
  * CHACHAPOLY 2 0x0054-0x0056
+ * PLATFORM  2 0x0080-0x0082
  *
  * High-level module nr (3 bits - 0x0...-0x7...)
  * Name      ID  Nr of Errors