catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia8f2ae95679f98f2fc3f32239bbf3b3578c35888
diff --git a/extensions/phal/fw_update_watch.cpp b/extensions/phal/fw_update_watch.cpp
index 2c6f813..b778734 100644
--- a/extensions/phal/fw_update_watch.cpp
+++ b/extensions/phal/fw_update_watch.cpp
@@ -91,7 +91,7 @@
             // Colect device tree data
             openpower::phal::fwupdate::exportDevtree();
         }
-        catch (fs::filesystem_error& e)
+        catch (const fs::filesystem_error& e)
         {
             log<level::ERR>(
                 fmt::format("Filesystem error reported Error:({})", e.what())