console: Fix flushing for slow consoles

Commit 266041f0e6 ("console: Add compile-time fast path when only
CBMEM console is used") introduced a typo when refactoring CBMEM console
fast path code that effectively causes consoles to never get flushed.
The fact that nobody complained in 3 years shows that the flush callback
is probably not that important for most consoles in practice. Still,
it's a pretty bad bug and should be fixed.

Change-Id: Ib9b96cb744447ccba99c4186540442b542914e01
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/89397
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/console/printk.c

@@ -143,7 +143,7 @@ int vprintk(int msg_level, const char *fmt, va_list args)
 	console_time_run();
 
 	i = vtxprintf(wrap_putchar, fmt, args, state.as_ptr);
-	if (LOG_FAST(state))
+	if (!LOG_FAST(state))
 		console_tx_flush();
 
 	console_time_stop();