Revert "Revert "Reapply "drm/nouveau/firmware: Fix SG_DEBUG error with nvkm_firmware_ctor()""

[Avenger-285714]

Reverts #315

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在nvkm_firmware_ctor函数中，fw->img的内存分配应该使用kmalloc而不是dma_alloc_coherent，以避免潜在的DMA错误。
• dma_map_single函数的使用应该检查返回值，以确保内存映射成功。
• kfree函数在内存映射失败时被调用，但是没有相应的注释说明为什么需要释放内存。
• sg_init_one函数的使用应该确保fw->img已经被正确映射到设备。

是否建议立即修改:
是

[deepin-ci-robot]

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