printk: remove zap_locks() function

We use printk-safe now which makes printk-recursion detection code
in vprintk_emit() unreachable. The tricky thing here is that, apart
from detecting and reporting printk recursions, that code also used
to zap_locks() in case of panic() from the same CPU. However,
zap_locks() does not look to be needed anymore:

1) Since commit 08d78658f393 ("panic: release stale console lock to
   always get the logbuf printed out") panic flushing of `logbuf' to
   console ignores the state of `console_sem' by doing
   	panic()
		console_trylock();
		console_unlock();

2) Since commit cf9b1106c81c ("printk/nmi: flush NMI messages on the
   system panic") panic attempts to zap the `logbuf_lock' spin_lock to
   successfully flush nmi messages to `logbuf'.

Basically, it seems that we either already do what zap_locks() used to
do but in other places or we ignore the state of the lock. The only
reaming difference is that we don't re-init the console semaphore in
printk_safe_flush_on_panic(), but this is not necessary because we
don't call console drivers from printk_safe_flush_on_panic() due to
the fact that we are using a deferred printk() version (as was
suggested by Petr Mladek).

Link: http://lkml.kernel.org/r/[email protected]
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Calvin Owens <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Peter Hurley <[email protected]>
Cc: [email protected]
Signed-off-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>

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