Update IfConfig.c to use TPL_CALLBACK instead of TPL_CALLBACK-1 to follow UEFI spec.
Update IfConfig.c to use TPL_CALLBACK instead of TPL_CALLBACK-1 to follow UEFI spec.

Signed-off-by: Star Zeng <5c6bb72efe464613af94e84c05522a361b23844a@intel.com>
Reviewed-by: Ruiyu Ni <9fa3a6894a36bca79e6a72ad65af5a5702efecd1@intel.com>
mruzicka/edk-shell,mruzicka/edk-shell