scripts/checkpatch.pl: device_initcall is not the only __initcall substitute

This patch adds a link to init.h to find appropriate initcall function to
replace obsolete __initcall

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>