LoongArch: BPF: Zero-extend signed ALU32 div/mod results

In the Linux kernel, the following vulnerability has been resolved: LoongArch: BPF: Zero-extend signed ALU32 div/mod results ALU32 operations write a 32-bit result and leave the upper 32 bits of the BPF register zero. The LoongArch JIT sign-extends the result of signed ALU32 BPF_DIV and BPF_MOD (off=1), so a negative 32-bit quotient or remainder leaves bits 63:32 set in JITted code while the verifier and interpreter model those bits as zero. Keep sign-extension on the operands, which signed divide needs, and zero-extend the ALU32 result after the divide or modulo instruction, matching the unsigned ALU32 div/mod paths and every other ALU32 operation in this JIT.