st/mesa: make sure to create a "clean" bool when doing i2b

st/mesa: make sure to create a "clean" bool when doing i2b

i2b has to work for all integers, not just 1. INEG would not necessarily
result with all bits set, which is something that other operations can
rely on by e.g. using AND (or INEG for b2i).

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Cc: mesa-stable@lists.freedesktop.org