printk: Fix warning about unused suppress_message_printing

printk: Fix warning about unused suppress_message_printing

suppress_message_printing() is not longer called in console_unlock().
Therefore it is not longer needed with disabled CONFIG_PRINTK.

This fixes the warning:

kernel/printk/printk.c:2033:13: warning: ‘suppress_message_printing’ defined but not used [-Wunused-function]
 static bool suppress_message_printing(int level) { return false; }

Reported-by: Stephen Rothwell <[email protected]>
Reported-by: Arnd Bergmann <[email protected]>
Suggested-by: Maninder Singh <[email protected]>
Acked-by: Sergey Senozhatsky <[email protected]>
Signed-off-by: Petr Mladek <[email protected]>