udf: convert to new aops

udf: convert to new aops

Convert udf to new aops.  Also seem to have fixed pagecache corruption in
udf_adinicb_commit_write -- page was marked uptodate when it is not.  Also,
fixed the silly setup where prepare_write was doing a kmap to be used in
commit_write: just do kmap_atomic in write_end.  Use libfs helpers to make
this easier.

Signed-off-by: Nick Piggin <[email protected]>
Cc: <[email protected]>
Cc: Jan Kara <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>