printk: Remove printk.h inclusion in percpu.h

After the commit 42a0bb3f71 ("printk/nmi: generic solution for safe
printk in NMI") the printk.h is not needed anymore in percpu.h.

Moreover `make headerdep` complains (an excerpt)

In file included from linux/printk.h,
                 from linux/dynamic_debug.h:188
                 from linux/printk.h:559 <-- here
                 from linux/percpu.h:9
                 from linux/idr.h:17
include/net/9p/client.h:13: warning: recursive header inclusion

Yeah, it's not a root cause of this, but removing will help to reduce
the noise.

Fixes: 42a0bb3f71 ("printk/nmi: generic solution for safe printk in NMI")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20211112140749.80042-1-andriy.shevchenko@linux.intel.com

include/linux/percpu.h

@@ -6,7 +6,6 @@
 #include <linux/preempt.h>
 #include <linux/smp.h>
 #include <linux/cpumask.h>
-#include <linux/printk.h>
 #include <linux/pfn.h>
 #include <linux/init.h>