remote.c: Cleanup unused variables

remote.c: Cleanup unused variables

I built remote.c with -Wunused, to check a function I was working on,
turns out there is a bunch of unused variables.

gdb/ChangeLog:

	* remote.c (remote_register_number_and_offset): Remove unused
	variable(s).
	(remote_thread_always_alive): Likewise.
	(remote_update_thread_list): Likewise.
	(process_initial_stop_replies): Likewise.
	(remote_start_remote): Likewise.
	(remote_check_symbols): Likewise.
	(discard_pending_stop_replies): Likewise.
	(process_stop_reply): Likewise.
	(putpkt_binary): Likewise.
	(getpkt): Likewise.
	(remote_add_target_side_condition): Likewise.
	(remote_insert_breakpoint): Likewise.
	(remote_supports_stopped_by_sw_breakpoint): Likewise.
	(remote_supports_stopped_by_hw_breakpoint): Likewise.
	(remote_xfer_partial): Likewise.
	(remote_read_btrace): Likewise.
	(remote_async_serial_handler): Likewise.
	(remote_thread_events): Likewise.
	(_initialize_remote): Likewise.