LoongArch: Add guard for the larch_insn_gen_xxx functions

Add guard for the larch_insn_gen_xxx functions to verify whether the
immediate operand is within the acceptable range.

Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
3 files changed