UefiPayloadPkg: Boot mode in PHIT HOB will not be updated

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4136



System will depend on Boot Mode value to do different behavior
Update during Capsule Update process. So UPL need to support
update boot mode.

Cc: Guo Dong <guo.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Reviewed-by: James Lu <james.lu@intel.com>
Reviewed-by: Gua Guo <gua.guo@intel.com>
Signed-off-by: VictorX Hsu <victorx.hsu@intel.com>