NFS: Fix for bug in handling of errors for O_DIRECT writes

Commit eda3cef8 ("NFS: Fix error
handling in nfs_direct_write_result()") ensured that if a WRITE returns
an error, then data->res.verf->committed is not tested (as it is not
initialised).

Then commit 60fa3f76

 ("NFS: Fix two bugs
in the O_DIRECT write code") inadvertently reverted this while fixing
other problems.

So move the test so that we never examine ->committed in an error case,
and fix a speeling error while we are there.

Cc: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>