printk: Make it compile with !CONFIG_PRINTK

Commit 3ccf3e830615 ("printk/sched: Introduce special
printk_sched() for those awkward moments") overlooked
an #ifdef, so move code around to respect these directives.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Link: http://lkml.kernel.org/r/1331811337.18960.179.camel@twins
Signed-off-by: Ingo Molnar <mingo@elte.hu>