9p: missing chunk of "fs/9p: Don't update file type when updating file attributes"

In commit 45089142 Aneesh had missed one (admittedly, very unlikely
to hit) case in v9fs_stat2inode_dotl().  However, the same considerations
apply there as well - we have no business whatsoever to change ->i_rdev
or the file type.

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