prefer std::format over fmt

Switch to std::format to remove the dependency on fmt.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id3a1295ba8a90fb756cfc500892dcc5b3235e27b
diff --git a/occ_command.hpp b/occ_command.hpp
index a8c5dd4..58d351a 100644
--- a/occ_command.hpp
+++ b/occ_command.hpp
@@ -3,13 +3,13 @@
 #include "occ_errors.hpp"
 #include "utils.hpp"
 
-#include <fmt/format.h>
-
 #include <org/open_power/OCC/PassThrough/server.hpp>
 #include <sdbusplus/bus.hpp>
 #include <sdbusplus/server/object.hpp>
 
+#include <format>
 #include <string>
+#include <utility>
 
 namespace open_power
 {
@@ -62,7 +62,7 @@
 
 static inline auto format_as(SysPwrMode spm)
 {
-    return fmt::underlying(spm);
+    return std::to_underlying(spm);
 }
 
 // Only some of the SysPwrModes are currently supported and allowed to be set
@@ -98,7 +98,7 @@
 
 static inline auto format_as(CmdStatus cs)
 {
-    return fmt::underlying(cs);
+    return std::to_underlying(cs);
 }
 
 /** @brief Trace block of data in hex with log<level:INFO>