* config/rx/rx-opts.h: New.
* config/rx/rx.c (rx_cpu_type): Remove.
(rx_handle_option): Don't assert that global structures are in
use. Access variables via opts pointer. Defer most handling of
OPT_mint_register_. Use error_at.
(rx_option_override): Handle deferred OPT_mint_register_ here.
* config/rx/rx.h (enum rx_cpu_types): Move to rx-opts.h.
* config/rx/rx.opt (config/rx/rx-opts.h: New HeaderInclude.
(mcpu=): Use Enum and specifiy rx_cpu_type with Var.
(rx_cpu_types): New Enum and EnumValue entries.
(mint-register=): Use Defer and use Var accordingly.