NFS/localio: remove -EAGAIN handling in nfs_local_doio()

NFS/localio: remove -EAGAIN handling in nfs_local_doio()

Handling -EAGAIN in nfs_local_doio() was introduced with commit
0978e5b85fc08 (nfs_do_local_{read,write} were made to have negative
checks for correspoding iter method) but commit e43e9a3a3d66
since eliminated the possibility for this -EAGAIN early return.

So remove nfs_local_doio()'s -EAGAIN handling that calls
nfs_localio_disable_client() -- while it should never happen from
nfs_do_local_{read,write} this particular -EAGAIN handling is now
"dead" and so it has become a liability.

Fixes: e43e9a3a3d66 ("nfs/localio: refactor iocb initialization")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>