switch fmt::format to use std::format

fmt::format is supported in the c++ std. This will
help to remove fmt package dependency.

Change-Id: Ia3f5c607a348f062a0f112d5eae8b51ecc23fd37
Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
diff --git a/procedures/p9/enter_mpreboot.cpp b/procedures/p9/enter_mpreboot.cpp
index 301bf7d..048f101 100644
--- a/procedures/p9/enter_mpreboot.cpp
+++ b/procedures/p9/enter_mpreboot.cpp
@@ -22,12 +22,12 @@
 #include <libpdbg_sbe.h>
 }
 
-#include <fmt/format.h>
 #include <sys/wait.h>
 #include <unistd.h>
 
 #include <phosphor-logging/log.hpp>
 
+#include <format>
 #include <system_error>
 #include <vector>
 
@@ -53,7 +53,7 @@
     }
 
     log<level::INFO>(
-        fmt::format("Enter MPIPL completed on proc({})", pdbg_target_index(tgt))
+        std::format("Enter MPIPL completed on proc({})", pdbg_target_index(tgt))
             .c_str());
 }