nir: Zero out texture instructions when creating them.

There are so many flags in textures, that the CSE pass would have a hard
time referencing the correct set when figuring out if two texture ops are
the same.  By zeroing, we can avoid that fragility.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

src/glsl/nir/nir.c

@@ -450,7 +450,7 @@ nir_call_instr_create(nir_shader *shader, nir_function_overload *callee)
 nir_tex_instr *
 nir_tex_instr_create(nir_shader *shader, unsigned num_srcs)
 {
-   nir_tex_instr *instr = ralloc(shader, nir_tex_instr);
+   nir_tex_instr *instr = rzalloc(shader, nir_tex_instr);
    instr_init(&instr->instr, nir_instr_type_tex);
 
    dest_init(&instr->dest);