nfsd: Fix a memory leak in an error handling path

nfsd: Fix a memory leak in an error handling path

[ Upstream commit 6a6eaa555f88d1d419caed2d48a06efd1de6ce1c ]

If this memdup_user() call fails, the memory allocated in a previous call
a few lines above should be freed. Otherwise it leaks.

Fixes: f50edfb1b698 ("nfsd: add support for upcall version 2")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>