rxrpc: Use refcount_t rather than atomic_t

[ Upstream commit a0575429 ]

Move to using refcount_t rather than atomic_t for refcounts in rxrpc.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: 3bcd6c7e ("rxrpc: Fix race between conn bundle lookup and bundle removal [ZDI-CAN-15975]")
Signed-off-by: Sasha Levin <sashal@kernel.org>