etnaviv: SINGLE_BUFFER support on GC3000

etnaviv: SINGLE_BUFFER support on GC3000

This patch adds support for the SINGLE_BUFFER feature on GC3000
GPUs, which allows rendering to a single buffer using multiple pixel
pipes.

This feature is always used when it is available, which means that
multi-tiled formats are no longer being used in that case, and all
buffers will be normal (super)tiled. This mimics the behavior of the
blob on GC3000.

- Because the same format can be used to render to and texture from,
  this avoids an extra resolve pass when rendering to texture.

- i.MX6qp includes a PRE which can scan-out directly from tiled formats,
  avoiding untiling overhead.

Signed-off-by: Wladimir J. van der Laan <laanwj@gmail.com>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>