SUNRPC: Replace internal use of SOCKWQ_ASYNC_NOSPACE

[ Upstream commit 2790a624d43084de590884934969e19c7a82316a ]

The socket's SOCKWQ_ASYNC_NOSPACE can be cleared by various actors in
the socket layer, so replace it with our own flag in the transport
sock_state field.

Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Stable-dep-of: 4db9ad82a6c8 ("sunrpc: clear XPRT_SOCK_UPD_TIMEOUT when reset transport")
Signed-off-by: Sasha Levin <sashal@kernel.org>