[ros-diffs] [arty] 29928: Fix memory map to kernel mode. Allow prep serial in kdcom (and stop clobbering the data miss handler). Clean up boot mapping a bit. Silence some boot time spam. Enable not present page handler (yes, this routing actually works). Scan physical memory on the (virtually 100%) chance that open firmware will somehow have a buggy implementation of the memory object, or we're on prep hardware. Initialize syscall trap early, so we can do DbgPrint.