UefiCpuPkg: Remove the absolute address jump in LoongArch exception handler

In LoongArch, the last ABS reloaction is located in the exception
vector. Use four placeholder instructions and patch the addresses in
these four instructions after copying vector code.

It have no ABS relocation since this patch, which is good for other
compilers(such as clang).

Signed-off-by: Chao Li <lichao@loongson.cn>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: Dun Tan <dun.tan@intel.com>
Cc: Arun Subramanian Baskaran <arun.subramanian.baskaran@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eduardo Cuevas Farfan <eduardo.cuevas.farfan@intel.com>