LoongArch: Fix potential ADE in loongson_gpu_fixup_dma_hang()

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Linux kernel 安全漏洞

The Linux kernel is the core of the open-source operating system Linux, developed by the Linux Foundation in the United States. There is a security vulnerability in the Linux kernel, which stems from an issue with the switch case statement in the loongsongpufixupdmahang function within LoongArch...