usb: typec: tcpm: implement retry mechanism for Discover Identity VDMs

The current mechanism for sending Discover Identity in the ready state
presents a flaw where tcpm_queue_vdm can collide with non interruptible
AMSes such as GET_SINK_CAP or VCONN_SWAP. vdm_run_state_machine will hit
the VDM_STATE_BUSY state, and Discover SVIDs or Discover Modes will not
retry.

This patch introduces a state machine under the enum vdm_discovery_states.
The tcpm_port field vdm_discovery_state tracks which step of the Discover
Identity process has been completed.

The current TCPM implementation utilizes the send_discover and
send_discover_prime booleans to queue Discover Identity in the
aforementioned collision case. These booleans are removed in place of
vdm_discovery_state and send_discover_work is replaced by
vdm_discovery_work, which runs unconditionally in the ready state.
When the Discovery process is complete, the port will move to the
VDM_DISCOVERY_COMPLETE state and vdm_discovery_work becomes a no-op.
When there are still Discovery VDMs to be sent, vdm_discovery_work will
continue based on the last received response from the port partner or
cable.

Signed-off-by: RD Babiera <rdbabiera@google.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Badhri Jagan Sridharan <badhri@google.com>
Link: https://patch.msgid.link/20260717232612.3671978-2-rdbabiera@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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