udf: Set i_generation field

Currently UDF doesn't initialize i_generation in any way and thus NFS
can easily get reallocated inodes from stale file handles. Luckily UDF
already has a unique object identifier associated with each inode -
i_unique. Use that for initialization of i_generation.

Signed-off-by: Jan Kara <jack@suse.cz>

diff --cc fs/udf/ialloc.c
Simple merge

diff --cc fs/udf/inode.c
Simple merge