r600: use ieee version of rcp

r600: use ieee version of rcp

r600 used the clamped version for rcp, whereas both evergreen and cayman
used the ieee version. I don't know why that discrepancy exists (it does so
since day 1) but there does not seem to be a valid reason for this, so make
it consistent. This seems now safer than before the previous commit (using
the dx10 clamp bit).
Note that rsq still uses clamped version (as before even though the table
may have suggested otherwise for evergreen) for r600/eg, but not for cayman.
Will be changed separately for better regression tracking...

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