LoongArch: Define ELF relocation types added in ABIv2.0

These relocation types are used by GNU binutils >= 2.40 and GCC >= 13.
Add their definitions so we will be able to use them in later patches.

Link: https://github.com/loongson/LoongArch-Documentation/pull/57
Tested-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>