Revert "printk: add kthread console printers"

This reverts commit 09c5ba0.

This reverts commit b87f023.

The testing of 5.19 release candidates revealed missing synchronization
between early and regular console functionality.

It would be possible to start the console kthreads later as a workaround.
But it is clear that console lock serialized console drivers between
each other. It opens a big area of possible problems that were not
considered by people involved in the development and review.

printk() is crucial for debugging kernel issues and console output is
very important part of it. The number of consoles is huge and a proper
review would take some time. As a result it need to be reverted for 5.19.

Link: https://lore.kernel.org/r/YrBdjVwBOVgLfHyb@alley
Signed-off-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

include/linux/console.h

@@ -153,8 +153,6 @@ struct console {
 	uint	ospeed;
 	u64	seq;
 	unsigned long dropped;
-	struct task_struct *thread;
-
 	void	*data;
 	struct	 console *next;
 };