r600g: merge the TXQ and BUFFER constant buffers (v1.1)

r600g: merge the TXQ and BUFFER constant buffers (v1.1)

We are using 1 more buffer than we have, although in the future the
driver should just end up using one buffer in total probably, this
is a good first step, it merges the txq cube array and buffer info
constants on r600 and evergreen.

This should in theory fix geom shader tests on r600.

v1.1: fix comments from Glenn.

Reviewed-by: Glenn Kennard <glenn.kennard@gmail.com>
Cc: "10.4 10.3" <mesa-stable@lists.freedesktop.org
Signed-off-by: Dave Airlie <airlied@redhat.com>