SUNRPC: Use struct xdr_stream when decoding RPC Reply header

mainline inclusion
from mainline-v5.1-rc1
commit a0584ee9
category: bugfix
bugzilla: 13061
CVE: NA

-----------------------------------------------

Modernize and harden the code path that parses an RPC Reply
message.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Conflict:
	include/linux/sunrpc/auth.h
	include/linux/sunrpc/xdr.h
	net/sunrpc/auth.c
	net/sunrpc/auth_gss/auth_gss.c
	net/sunrpc/auth_null.c
	net/sunrpc/clnt.c
Partly merged because it can fix xfstests generic/095 failed with WARN_ON
when call_decode.
eb90a16e ("SUNRPC: rpc_decode_header() must always return a non-zero
value on error") is not needed because we not merge the code:
	error = rpcauth_checkverf(task, xdr)

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>