Use the offload transmit queue to set flags on TLS connections.

Requests to modify the state of TLS connections need to be sent on the
same queue as TLS record transmit requests to ensure ordering.

However, in order to use the offload transmit queue in t4_set_tcb_field(),
the function needs to be updated to do proper flow control / credit
management when queueing a request to an offload queue. This required
passing a pointer to the toepcb itself to this function, so while here
remove the 'tid' and 'iqid' parameters and obtain those values from the
toepcb in t4_set_tcb_field() itself.

Submitted by: Harsh Jain @ Chelsio (original version)
Reviewed by: np
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D14871