nv50/ir: fix SUSTx constraints on Kepler

nv50/ir: fix SUSTx constraints on Kepler

To prevent out-of-bounds access and format mismatch we add a predicate
on sustp, but we have to account for it when the sources are condensed
because a predicate is a source. Using the range 3:6 will only condense
the input data and it's always the case. This also fixes constraints
when an indirect access is used.

This ensures that sources are correctly aligned.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>