x509_crt: Adjusted the len of lpMultiByteStr arg in WideCharToMultiByte

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 162281d..4418dab 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1585,8 +1585,7 @@
             continue;
         }
         w_ret = WideCharToMultiByte(CP_ACP, 0, file_data.cFileName,
-                                    -1, p, (int) len - 1,
-                                    NULL, NULL);
+                                    -1, p, (int) len, NULL, NULL);
         if (w_ret == 0) {
             ret = MBEDTLS_ERR_X509_FILE_IO_ERROR;
             goto cleanup;