console: Allow using vprintk() with disabled console

The prototype of vprintk() is currently declared unconditionally, which
prevents it from being used in situations where the console is disabled.
The code will compile correctly, but not link, since the definition in
console.c isn't being provided. This adds a shim around the declaration
so that, like printk(), a call to vprintk() in this situation will expand
to a no-op function instead.

Change-Id: Ib4a9aa96a5b9dbb9b937ff45854bf6a407938b37
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/33181
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/console/printk.c

@@ -45,7 +45,7 @@ static void wrap_putchar_cbmemc(unsigned char byte, void *data)
 	__cbmemc_tx_byte(byte);
 }
 
-int vprintk(int msg_level, const char *fmt, va_list args)
+int do_vprintk(int msg_level, const char *fmt, va_list args)
 {
 	int i, log_this;
 
@@ -91,7 +91,7 @@ int do_printk(int msg_level, const char *fmt, ...)
 	int i;
 
 	va_start(args, fmt);
-	i = vprintk(msg_level, fmt, args);
+	i = do_vprintk(msg_level, fmt, args);
 	va_end(args);
 
 	return i;