init/main.c: fix warning: 'calltime.tv64' may be used uninitialized

Using:

	gcc (GCC) 4.5.0 20100610 (prerelease)

The following warning appears:

	init/main.c: In function `do_one_initcall':
	init/main.c:730:10: warning: `calltime.tv64' may be used uninitialized in this function

This warning is actually correct, as the global initcall_debug could
arguably be changed by the initcall.

Correct this warning by extracting a new function, do_one_initcall_debug,
that performs the initcall for the debug case.

Signed-off-by: Kevin Winchester <kjwinchester@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>