mesa/st: always use normalized coords for samplers

Normalized samplers is the norm, and non-normalized samplers might cause
some drivers and hardware to have to bend over backwards a bit.

We're using TXF here anyway, so it doesn't really matter what we set
this state to. So let's always use normalized samplers instead of
always using non-normalized samplers. That makes things easier for
everyone.

Fixes: 41e093fc98c ("st/pbo: add a fast pbo download code-path")
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17708>