nfs_common: factor out nfs_errtbl and nfs_stat_to_errno

nfs_common: factor out nfs_errtbl and nfs_stat_to_errno

[ Upstream commit 4806ded4c14c5e8fdc6ce885d83221a78c06a428 ]

Common nfs_stat_to_errno() is used by both fs/nfs/nfs2xdr.c and
fs/nfs/nfs3xdr.c

Will also be used by fs/nfsd/localio.c

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Stable-dep-of: c6c209ceb87f ("NFSD: Remove NFSERR_EAGAIN")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>