Remove undefined behavior

The commit here:
https://gerrit.openbmc-project.xyz/c/openbmc/meta-phosphor/+/39481

Located this issue.  open needs to be called with permissions, otherwise
it results in undefined behavior.

Tested:
Code now compiles with security flags enabled.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I597c5dff37a4e89af9a68f264782ada973c70622
diff --git a/oem/ibm/libpldmresponder/file_io_type_cert.cpp b/oem/ibm/libpldmresponder/file_io_type_cert.cpp
index b49903c..f21cdf2 100644
--- a/oem/ibm/libpldmresponder/file_io_type_cert.cpp
+++ b/oem/ibm/libpldmresponder/file_io_type_cert.cpp
@@ -116,11 +116,11 @@
     }
     if (certType == PLDM_FILE_TYPE_SIGNED_CERT)
     {
-        fileFd = open(clientCertPath, flags);
+        fileFd = open(clientCertPath, flags, S_IRUSR | S_IWUSR);
     }
     else if (certType == PLDM_FILE_TYPE_ROOT_CERT)
     {
-        fileFd = open(rootCertPath, flags);
+        fileFd = open(rootCertPath, flags, S_IRUSR | S_IWUSR);
     }
     if (fileFd == -1)
     {