glsl_to_tgsi: fix dst register for texturing fetches.

glsl_to_tgsi: fix dst register for texturing fetches.

I've no idea why there isn't a piglit that triggers this behaviour,
but while enabling TBOs for softpipe and r600g, I noticed all the
integer tests failed. I tracked it back to the TXF returning a float
when it should be returning an int. This fixed it and I haven't
seen any regressions in a full piglit run on softpipe.

http://bugs.freedesktop.org/55010

NOTE: This is a candidate for the 9.0 branch.

Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit 9785ae0973cc206afc36dbc7d5b9553f92d06b47)