fs/nfs: Use fatal_signal_pending instead of signal_pending

fs/nfs: Use fatal_signal_pending instead of signal_pending

commit bb002388901151fe35b6697ab116f6ed0721a9ed upstream.

We set the state of the current process to TASK_KILLABLE via
prepare_to_wait(). Should we use fatal_signal_pending() to detect
the signal here?

Fixes: b4868b44c562 ("NFSv4: Wait for stateid updates after CLOSE/OPEN_DOWNGRADE")
Signed-off-by: zhouchuangao <zhouchuangao@vivo.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>