Pull 9p regression fix from Al Viro:
"Fix for breakage introduced when switching p9_client_{read,write}() to
struct iov_iter * (went into 4.1)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
9p: ensure err is initialized to 0 in p9_client_read/write