PEL: Add function to generate unique PEL IDs

Create generatePELID() to return a unique 4B PEL ID every time it is
called. It will start at a base value, and then increment by 1 each
time.  It uses a file to save the next value to use.

This will be used by the PEL handling code to create unique values
for the error log ID field in the Private Header section.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I841a8dcc5dc48e2b663004be3dccfb114ba366f2
diff --git a/extensions/openpower-pels/paths.cpp b/extensions/openpower-pels/paths.cpp
new file mode 100644
index 0000000..dab73c9
--- /dev/null
+++ b/extensions/openpower-pels/paths.cpp
@@ -0,0 +1,23 @@
+#include "config.h"
+
+#include "paths.hpp"
+
+#include <filesystem>
+
+namespace openpower
+{
+namespace pels
+{
+
+namespace fs = std::filesystem;
+
+fs::path getPELIDFile()
+{
+    fs::path logIDPath{EXTENSION_PERSIST_DIR};
+    logIDPath /= fs::path{"pels"} / fs::path{"pelID"};
+    return logIDPath;
+}
+
+} // namespace pels
+
+} // namespace openpower