The device can be selected by GPU name or index. For example,
ffplay -hwaccel cuda \
-vulkan_params device="NVIDIA GeForce RTX 3060" \
foo.mp4
ffplay -hwaccel cuda -vulkan_params device="0" foo.mp4
Please note that select device by index only supported by hwcontext,
not by libplacebo.
Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>