autodetect_raid: add missing __init marking

The function autodetect_raid is only used by __init functions, and it refers
to __initdata, so it needs __init markings.  Fixes this error:
The function autodetect_raid() references
the variable __initdata raid_noautodetect.
This is often because autodetect_raid lacks a __initdata
annotation or the annotation of raid_noautodetect is wrong.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>