nir: Initialize nir_register::divergent

Fixes: c7fc44f9eb ("nir/from_ssa: Respect and populate divergence information")
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14205>

src/compiler/nir/nir.c

@@ -238,6 +238,7 @@ reg_create(void *mem_ctx, struct exec_list *list)
    reg->num_components = 0;
    reg->bit_size = 32;
    reg->num_array_elems = 0;
+   reg->divergent = false;
 
    exec_list_push_tail(list, &reg->node);