loongarch: Switch to software render when using LG100 series

[HecaiYuan]

CPU acceleration runs faster than integrated graphics on Loongson at present. @slouken @madebr

[slouken]

Is this something that's likely to be improved in the future? We generally don't add SDL workarounds for buggy drivers, instead we rely on the upstream project to fix their bugs.

This kind of hack will also prevent someone who wants to use SDL to verify performance of improved drivers.

I'm inclined not to accept this change. If people really want to force software rendering, they can set the environment variable SDL_RENDER_DRIVER=software

[jinboson]

Thanks for your clarification. It's NOT bugs of LG100 series, which is just not very good in performance when using them to render videos on some GPU-heavy applications. The coming LG200 series has improved a lot in performance, which does not need these changes any way. And the initial intention was to switch to software render by detecting not by manually setting something else. We thought that it was not good for users to do that. But we respect your decision.

[slouken]

I'll leave this open for consideration.

[slouken]

After consideration, I'll go ahead and merge this, thanks!