kernel/cpu.c: convert printk to pr_foo()

kernel/cpu.c: convert printk to pr_foo()

no level printk converted to pr_warn (if err)
no level printk converted to pr_info (disabling non-boot cpus)
Other printk converted to respective level.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>