serial: earlycon: prefer EARLYCON_DECLARE() variant

If a driver exposes early consoles with EARLYCON_DECLARE() and
OF_EARLYCON_DECLARE(), pefer the non-OF variant if the user specifies it
by
earlycon=<driver>,<options>

The rationale behind this is that some drivers register multiple setup
functions under the same driver name. Eg.

OF_EARLYCON_DECLARE(lpuart, "fsl,vf610-lpuart", lpuart_early_console_setup);
OF_EARLYCON_DECLARE(lpuart32, "fsl,ls1021a-lpuart", lpuart32_early_console_setup);
OF_EARLYCON_DECLARE(lpuart32, "fsl,imx7ulp-lpuart", lpuart32_imx_early_console_setup);
EARLYCON_DECLARE(lpuart, lpuart_early_console_setup);
EARLYCON_DECLARE(lpuart32, lpuart32_early_console_setup);

It depends on the order of the entries which console_setup() actually
gets called. To make things worse, I guess it also depends on the
compiler how these are ordered. Thus always prefer the EARLYCON_DECLARE()
ones.

Signed-off-by: Michael Walle <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/earlycon.c

···
 int __init setup_earlycon(char *buf)
 {
 	const struct earlycon_id **p_match;
+	bool empty_compatible = true;
 
 	if (!buf || !buf[0])
 		return -EINVAL;
···
 	if (early_con.flags & CON_ENABLED)
 		return -EALREADY;
 
+again:
 	for (p_match = __earlycon_table; p_match < __earlycon_table_end;
 	     p_match++) {
 		const struct earlycon_id *match = *p_match;
 		size_t len = strlen(match->name);
 
 		if (strncmp(buf, match->name, len))
+			continue;
+
+		/* prefer entries with empty compatible */
+		if (empty_compatible && *match->compatible)
 			continue;
 
 		if (buf[len]) {
···
 			buf = NULL;
 
 		return register_earlycon(buf, match);
+	}
+
+	if (empty_compatible) {
+		empty_compatible = false;
+		goto again;
 	}
 
 	return -ENOENT;