i965/fs: Use a default Y coordinate of 0 for TXF on gen9+

i965/fs: Use a default Y coordinate of 0 for TXF on gen9+

Previously, we were incrementing length but not actually putting anything
in the Y coordinate.  This meant that 1-D TXF operations had a garbage
array index.  If the surface is emitted as 1-D non-array, the coordinate
gets discarded and it works fine.  If it happens to be bound as an array
surface, it may count as an out-of-bounds array access and you get zero.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Cc: "11.1 11.2 12.0" <mesa-stable@lists.freedesktop.org>