tgsi: add interpolation location modifier support to text parser

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nv50,nvc0: remove hacky global per-sample interpolation setting

Now that inputs are correctly annotated with interpolation location,
don't try to divine whether all inputs should be per-sample-interpolated
or not.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0: do quadops on the right texture coordinates for TXD

handleTEX moves the layer as the first argument. This makes sure that
the quadops deal with the texture coordinates.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: <mesa-stable@lists.freedesktop.org>