fs/affs/inode.c: remove double extern affs_symlink_inode_operations

affs_symlink_inode_operations was already declared extern in affs.h

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>