vt: use TERMINAL_DECLARE_EARLY() macro

[mhorne]

Summary

It simplifies the declaration of the driver structures a little. There
are no current consumers of this macro, in fact it looks like it was
added for exactly this purpose.

This decreases the scope of some variables, so rework vt_init_logos()
such that it doesn't require them.

No functional change intended.

Test Plan

Build and boot kernel with CPU splash logos enabled.

[mhorne]

For reference:

#define	TERMINAL_DECLARE_EARLY(name, class, softc)			\
	static struct terminal name = {					\
		.tm_class = &class,					\
		.tm_softc = softc,					\
		.tm_flags = TF_CONS,					\
	};								\
	CONSOLE_DEVICE(name ## _consdev, termcn_cnops, &name)

#define	CONSOLE_DEVICE(name, ops, arg)					\
	static struct consdev name = {					\
		.cn_ops = &ops,						\
		.cn_arg = (arg),					\
	};								\
	DATA_SET(cons_set, name)

sys/dev/vt/vt_core.c

273

We lose this explicit initialization of cn_name, but it gets set to the same in vtterm_cnprobe().

[mhorne]

Does this seem okay @emaste? This was a drive-by cleanup I made a while ago when reading some code; I found it on a stale local branch but there's no larger motivation.