Poison Bit Forwarding to AXI

If poisoned bit forwarding is enabled in the AXI features control register, the poisoned TLP is flagged in the AWUSER bit [43]. Additionally, the PCIe Controller adds a message interface bit to indicate when a poisoned TLP is forwarded to the message interface.

The MASTER_AXI_BUSER is added to send a UR completion for poisoned non-posted write responses. You need to set this bit along with the write response if the non-posted write request had a poisoned TLP bit set in bit 43 of TARGET_AXI_AWUSER.