AXI WVALID before AWVALID

The AXI slave could either accept that W transfer by asserting WREADY, and then hold it in a buffer until it knows what address to store the data in, or it can stall the W transfer by holding WREADY low until it samples AWVALID asserted.

The AXI slave could either accept that W transfer by asserting WREADY, and then hold it in a buffer until it knows what address to store the data in, or it can stall the W transfer by holding WREADY low until it samples AWVALID asserted.