MdeModulePkg/DxeIpl: Support Capsule On Disk.

MdeModulePkg/DxeIpl: Support Capsule On Disk.

https://github.com/tianocore/tianocore.github.io/wiki/UEFI-Capsule-
on-Disk-Introducation

If Capsule On Disk mode, call Capsule On Disk Load PPI to load
capsules. When it fails, still goes to Firmware Update boot path.
BDS will clear corresponding indicator and reboot later on.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Chao B Zhang <chao.b.zhang@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
Reviewed-by: Chao B Zhang <chao.b.zhang@intel.com>