drm/nouveau/acr: Use kmemdup instead of kmalloc and memcpy

Fixes coccicheck warning:

drivers/gpu/drm/nouveau/nvkm/subdev/acr/hsfw.c:103:23-30: WARNING opportunity for kmemdup
drivers/gpu/drm/nouveau/nvkm/subdev/acr/hsfw.c:113:22-29: WARNING opportunity for kmemdup

Fixes: 22dcda45

 ("drm/nouveau/acr: implement new subdev to replace "secure boot"")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>