util/ra: Make allocating conflict lists optional

util/ra: Make allocating conflict lists optional

Since i965 is now using make_reg_conflicts_transitive and doesn't need
q-value computations, they are disabled on i965.  They are enabled
everywhere else so that they get the old behavior.  This reduces the time
spent in eglInitialize() on BDW by around 10-15%.

Reviewed-by: Eric Anholt <eric@anholt.net>