Implement PSA ITS over files

Implement the PSA ITS API over stdio files.

include/mbedtls/config.h

@@ -2794,6 +2794,18 @@
  */
 //#define MBEDTLS_PSA_CRYPTO_STORAGE_ITS_C
 
+/**
+ * \def MBEDTLS_PSA_ITS_FILE_C
+ *
+ * Enable the emulation of the Platform Security Architecture
+ * Internal Trusted Storage (PSA ITS) over files.
+ *
+ * Module:  library/psa_its_file.c
+ *
+ * Requires: MBEDTLS_FS_IO
+ */
+#define MBEDTLS_PSA_ITS_FILE_C
+
 /**
  * \def MBEDTLS_RIPEMD160_C
  *