Fix typo in arch/powerpc/boot/flatdevtree_env.h.
There is no Documentation/networking/ixgbe.txt.

README.cycladesZ is now in Documentation/.
wavelan.p.h is now in drivers/net/wireless/.
HFS.txt is now Documentation/filesystems/hfs.txt.
OSS-files are now in sound/oss/.
Signed-off-by: NJohann Felix Soden <johfel@users.sourceforge.net>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>