ufs: move calculation of offsets into ufs_getfrag_block()

... and massage ufs_frag_map() to take those instead of fragment number.

As it is, we duplicate the damn thing on the write side, open-coded and
bloody hard to follow.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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