accel/qaic: Flush the transfer list again

Before calling synchronize_srcu() we clear the transfer list, this is to
allow all the QAIC_WAIT_BO callers to exit otherwise the system could
deadlock. There could be a corner case where more elements get added to
transfer list after we have flushed it. Re-flush the transfer list once
all the holders of dbc->ch_lock have completed execution i.e.
synchronize_srcu() is complete.

Fixes: ff13be8 ("accel/qaic: Add datapath")
Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230517193540.14323-4-quic_jhugo@quicinc.com

Author: Pranjal Ramajor Asha Kanojiya

drivers/accel/qaic/qaic_data.c

@@ -1845,6 +1845,11 @@ void wakeup_dbc(struct qaic_device *qdev, u32 dbc_id)
 	dbc->usr = NULL;
 	empty_xfer_list(qdev, dbc);
 	synchronize_srcu(&dbc->ch_lock);
+	/*
+	 * Threads holding channel lock, may add more elements in the xfer_list.
+	 * Flush out these elements from xfer_list.
+	 */
+	empty_xfer_list(qdev, dbc);
 }
 
 void release_dbc(struct qaic_device *qdev, u32 dbc_id)