SUNRPC: Use BIT() macro in rpc_show_xprt_state()

[ Upstream commit 76497b1a

 ]

Clean up: BIT() is preferred over open-coding the shift.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>