The original restriction to UniformBuffer was due to the GL backend
where there is no GL buffer object for QRhiBuffers with usage
UniformBuffer. However, we can still implement this for cases when
there is a true GL buffer object underneath. With other backends it
should all work as-is already.
This becomes useful when one has buffers with usage Vertex that need
full updates every frame. (f.ex. instance data)
Unfortunately this involves renaming the function. But while at it, add
an autotest case as well.
Change-Id: Iff59e4509a8bae06654cc92fe8428bd79eb012fb
Reviewed-by: Andy Nichols <andy.nichols@qt.io>
2189e0f2fc