NFSD: Fix NFSv4's PUTPUBFH operation

According to RFC 8881, all minor versions of NFSv4 support PUTPUBFH.

Replace the XDR decoder for PUTPUBFH with a "noop" since we no
longer want the minorversion check, and PUTPUBFH has no arguments to
decode. (Ideally nfsd4_decode_noop should really be called
nfsd4_decode_void).

PUTPUBFH should now behave just like PUTROOTFH.

Reported-by: Cedric Blancher <cedric.blancher@gmail.com>
Fixes: e1a90ebd ("NFSD: Combine decode operations for v4 and v4.1")
Cc: Dan Shelton <dan.f.shelton@gmail.com>
Cc: Roland Mainz <roland.mainz@nrubsig.org>
Cc: stable@vger.kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>