openpower-pels: clean up various compile warnings

Compile warnings observed when compiling parts of the
openpower-pels (or corresponding tests) under stricter
compiler warning flags of Meson.

Issues fixed:
    - many unused parameters
    - invalid case fall-through
    - excess semi-colons
    - incorrect 'const' on return-by-value type
    - removal of variable length array in test case
    - uncaught return from 'system' call in test case

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8af69184042cf8661d1307a02ecf3afcab4724a1
diff --git a/extensions/openpower-pels/section.hpp b/extensions/openpower-pels/section.hpp
index 15ddcff..64bcda3 100644
--- a/extensions/openpower-pels/section.hpp
+++ b/extensions/openpower-pels/section.hpp
@@ -68,9 +68,9 @@
      * representation, this would return the string for it.
      */
     virtual std::optional<std::string>
-        getJSON(message::Registry& registry,
-                const std::vector<std::string>& plugins,
-                uint8_t creatorID) const
+        getJSON(message::Registry& /*registry*/,
+                const std::vector<std::string>& /*plugins*/,
+                uint8_t /*creatorID*/) const
     {
         return std::nullopt;
     }
@@ -83,8 +83,8 @@
      * representation, this would return the string for it.
      */
     virtual std::optional<std::string>
-        getJSON(uint8_t creatorID,
-                const std::vector<std::string>& plugins) const
+        getJSON(uint8_t /*creatorID*/,
+                const std::vector<std::string>& /*plugins*/) const
     {
         return std::nullopt;
     }
@@ -103,7 +103,7 @@
      *
      * @return bool - true if successful, false else
      */
-    virtual bool shrink(size_t newSize)
+    virtual bool shrink(size_t /*newSize*/)
     {
         return false;
     }