lockdep, UML: fix compilation when CONFIG_TRACE_IRQFLAGS_SUPPORT is not set

Hiroshi Shimamoto reported:

> > !TRACE_IRQFLAGS_SUPPORT mode of build for future work, it can be
> > restored via a simple revert.
>
> Hi, it seems that this patch breaks uml build.
>
> kernel/printk.c: In function 'vprintk':
> kernel/printk.c:674: error: implicit declaration of function
> 'raw_local_irq_save' kernel/printk.c:772: error: implicit declaration of
> function 'raw_local_irq_restore'

With the patch bellow it compiles (make ARCH=um with a x86 host), but I'm
really out of my league on this one...

Reported-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>