glsl_to_tgsi: add SVIEW decl support

glsl_to_tgsi: add SVIEW decl support

Freedreno needs sampler type information to deal with int/uint textures.
To accomplish this, start creating sampler-view declarations, as
suggested here:

 http://lists.freedesktop.org/archives/mesa-dev/2014-November/071583.html

create a sampler-view with index matching the sampler, to encode the
texture type (ie. SINT/UINT/FLOAT).  Ie:

   DCL SVIEW[n], 2D, UINT
   DCL SAMP[n]
   TEX OUT[1], IN[1], SAMP[n]

For tgsi texture instructions which do not take an explicit SVIEW
argument, the SVIEW index is implied by the SAMP index.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>