nvc0/ir: fix picking of coordinates from tex instruction for textureGrad

nvc0/ir: fix picking of coordinates from tex instruction for textureGrad

On Fermi, there's an argument in front of the coords that combines array
and indirect handle, while on Kepler the array and the indirect handle
are separate (and in front of the coords). We were previously only
accounting for the array bit of it, if there were an indirect access it
wouldn't be counted in the formula.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: "11.1 11.2" <mesa-stable@lists.freedesktop.org>