Correctly flip textures in DrawActiveTexture()

We want to flip the origin of UV (top to bottom), not the pixels within the specified range.

The flip value isn't used by any of the new calls in #6049, so I don't think anything needs the "flip the specified area" behavior.

This fixes Wild Arms XF (which has 512x512 framebuffers and needs to render only the top half.)

-[Unknown]