enhance the initcall_debug boot option:

 - measure the time the initcall took to execute and report
   it in units of milliseconds.

 - show the return code of initcalls (useful to see failures and
   to make sure that an initcall hung)

[akpm@linux-foundation.org: fix printk warning]
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>