9p: fix put_data error handling

Abhishek Kulkarni pointed out an inconsistency in the way
errors are returned from p9_put_data.  On deeper exploration it
seems the error handling for this path was completely wrong.
This patch adds checks for allocation problems and propagates
errors correctly.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 file changed