Fix incorrect texture load/store from buffer_t
Fix incorrect texture load/store from buffer_t

The host pointer represents the location of `min[i]` and is the start
of data, so the old code would read garbage memory with negative mins.

psuriana/Halide,jiawen/Halide,psuriana/Halide,jiawen/Halide,kgnk/Halide,jiawen/Halide,jiawen/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,psuriana/Halide,ronen/Halide,kgnk/Halide,ronen/Halide,kgnk/Halide,ronen/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,jiawen/Halide,ronen/Halide,ronen/Halide,jiawen/Halide,jiawen/Halide,psuriana/Halide,ronen/Halide,kgnk/Halide,kgnk/Halide