svga: Fix index buffer uploads

svga: Fix index buffer uploads

In the case of SWTNL and index translation we were uploading index buffers
and then reading out from them using the CPU. Furthermore, when translating
indices we often cached the results with an upload_mgr buffer, causing the
cached indexes to be immediately discarded on the next write to that
upload_mgr buffer.

Fix this by only uploading when we know the index buffer is going to be
used by hardware. If translating, only cache translated indices if the
original buffer was not a user buffer. In the latter case when we're not
caching, use an upload_mgr buffer for the hardware indices.

This means we can also remove the SWTNL hand-crafted index buffer upload
mechanism in favour of the upload_mgr.

Finally avoid using util_upload_index_buffer(). It wastes index buffer
space by trying to make sure that the offset of the indices in the
upload_mgr buffer is larger or equal to the position of the indices in
the source buffer. From what I can tell, the SVGA device does not
require that.

Testing done: Piglit quick. No regressions.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>