r600: use ieee version of rsq

r600: use ieee version of rsq

Both r600 and evergreen used the clamped version, whereas cayman used the
ieee one. I don't think there's a valid reason for this discrepancy, so let's
switch to the ieee version for r600 and evergreen too, since we generally
want to stick to ieee arithmetic.
With this, behavior for both rcp and rsq should now be the same for all of
r600, eg, cm, all using ieee versions (albeit note rsq retains the abs
behavior for everybody, which may not be a good idea ultimately).

Reviewed-by: Dave Airlie <airlied@redhat.com>