gk110/ir: emit load constant subop

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
gm107/ir: emit LDC subops

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: support 2d constbuf indexing

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
nvc0/ir: add kepler+ support for indirect texture references

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>