nv30/draw: switch varying hookup logic to know about texcoords

nv30/draw: switch varying hookup logic to know about texcoords

Commit 8acaf862dfe switched things over to use TEXCOORD instead of
GENERIC, but did not update the nv30 swtnl draw paths. This teaches the
draw logic about TEXCOORD.

Among other things, this fixes a crash in demos/arbocclude when using
swtnl. Curiously enough, the point-sprite piglit works without this.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: "10.5 10.6" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 25be70462dbb7ee994e69ffccc3de94e4114e667)