catch exceptions as const

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If6aba71f482f75143e6d669763b8853db22318cf
diff --git a/pmbus.cpp b/pmbus.cpp
index 3440667..5483ca4 100644
--- a/pmbus.cpp
+++ b/pmbus.cpp
@@ -98,7 +98,7 @@
         file.open(path);
         file >> name;
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         log<level::ERR>((std::string("Unable to read PMBus device name "
                                      "PATH=") +
@@ -147,7 +147,7 @@
             elog<InternalFailure>();
         }
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         auto rc = errno;
 
@@ -189,7 +189,7 @@
         file.open(path);
         file >> std::hex >> data;
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         auto rc = errno;
         log<level::ERR>((std::string("Failed to read sysfs file "
@@ -222,7 +222,7 @@
         file.open(path);
         file >> data;
     }
-    catch (std::exception& e)
+    catch (const std::exception& e)
     {
         auto rc = errno;
         log<level::ERR>((std::string("Failed to read sysfs file "