Fix long-standing bug in error code description
MBEDTLS_ERR_ASN1_INVALID_DATA is documented as "not used", but it has
been used since the PolarSSL days.
diff --git a/include/mbedtls/asn1.h b/include/mbedtls/asn1.h
index 6891bb9..92f3bcb 100644
--- a/include/mbedtls/asn1.h
+++ b/include/mbedtls/asn1.h
@@ -52,7 +52,7 @@
#define MBEDTLS_ERR_ASN1_UNEXPECTED_TAG -0x0062 /**< ASN1 tag was of an unexpected value. */
#define MBEDTLS_ERR_ASN1_INVALID_LENGTH -0x0064 /**< Error when trying to determine the length or invalid length. */
#define MBEDTLS_ERR_ASN1_LENGTH_MISMATCH -0x0066 /**< Actual length differs from expected length. */
-#define MBEDTLS_ERR_ASN1_INVALID_DATA -0x0068 /**< Data is invalid. (not used) */
+#define MBEDTLS_ERR_ASN1_INVALID_DATA -0x0068 /**< Data is invalid. */
#define MBEDTLS_ERR_ASN1_ALLOC_FAILED -0x006A /**< Memory allocation failed */
#define MBEDTLS_ERR_ASN1_BUF_TOO_SMALL -0x006C /**< Buffer too small when writing ASN.1 data structure. */