mmc: Add update-bios-attr-table subcommand

Add the update-bios-attr-table subcommand to update the bios attribute
table with the host firmware well-known names based on system type. The
system type is provided by Entity Manager, and this new subcommand uses
some of the existing infrastructure that the process-host-firmware
subcommand has to determine the system type.

Add a new service file to run this new subcommand so that it can block
waiting for the entity manager interface to appear on D-Bus.

Subsequent commands will add parsing the JSON file to build the bios
attribute string and set the bios attribute property.

Change-Id: Iacee975e273bae562d2d42cd8b642b9d0744a121
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/functions.hpp b/functions.hpp
index f7511aa..b364393 100644
--- a/functions.hpp
+++ b/functions.hpp
@@ -45,5 +45,9 @@
 std::shared_ptr<void> processHostFirmware(
     sdbusplus::bus::bus&, std::map<std::string, std::vector<std::string>>,
     std::filesystem::path, ErrorCallbackType, sdeventplus::Event&);
+std::shared_ptr<void>
+    updateBiosAttrTable(sdbusplus::bus::bus&,
+                        std::map<std::string, std::vector<std::string>>,
+                        sdeventplus::Event&);
 } // namespace process_hostfirmware
 } // namespace functions