cxgbe tom: Handle a race condition when enabling TLS offload

Use a separate state for when a request to set RX_QUIESCE has been
sent but the resulting TCB reply has not been received. In
particular, this correctly handles the case where data has been
received and queued in the receive queue before the quiesce request
takes effect.

Reviewed by: np
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D44435

(cherry picked from commit 9978c6289d621ac9edc95acb4e0f527a62a49b03)