fs/9p: Invalidate dentry if inode type change detected in cached mode

This is an extension of the last commit to cached mode as well.  While
server-side changes when using cached mode is not expected, when it does
happen we can get things like -EOPNOTSUPP.  With this change at least when
we realize the inode has updated (for example after a `touch` on the
client), we can get a new one.

Signed-off-by: Tingmao Wang <m@maowtm.org>
Message-ID: <01afd3c77d5cda181780dc931baa8f3fc54562c8.1743956147.git.m@maowtm.org>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>