i965/fs: Don't use ir->lod_info.grad.dPd<x,y> in emit_texture_*.

i965/fs: Don't use ir->lod_info.grad.dPd<x,y> in emit_texture_*.

This drops a dependency on ir_texture objects.

v2 (Ken): Rename lod_components to grad_components, as it only has a
          meaningful value for ir_txd.  We could set it to 1 for TXL,
          but there's no real need.

Signed-off-by: Connor Abbott <connor.abbott@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>