[kernel] Conditionally add an isa-debugcon output to logger

There have been a number of incidents lately where I've needed to see
logs but have been working on init, and broken the log output of
srv.logger. This commit adds a debug console output to io port 0x6600
if enabled at the top of logger.cpp.

qemu.sh

@@ -75,7 +75,7 @@ if [[ -n $TMUX ]]; then
     if [[ -n $debug ]]; then
         tmux split-window -h "gdb ${debugtarget}" &
     else
-        tmux split-window -h -l 80 "sleep 1; telnet localhost 45455" &
+        tmux split-window -h -l 100 "sleep 1; telnet localhost 45455" &
         tmux last-pane
         tmux split-window -l 10 "sleep 1; telnet localhost 45454" &
     fi
@@ -91,9 +91,9 @@ qemu-system-x86_64 \
     -drive "if=pflash,format=raw,readonly,file=${assets}/ovmf/x64/ovmf_code.fd" \
     -drive "if=pflash,format=raw,file=${build}/ovmf_vars.fd" \
     -drive "format=raw,file=${build}/jsix.img" \
+    -chardev socket,host=localhost,port=45455,server,nowait,telnet=on,id=jsix_debug -device isa-debugcon,iobase=0x6600,chardev=jsix_debug \
     -monitor telnet:localhost:45454,server,nowait \
     -serial stdio \
-    -serial telnet:localhost:45455,server,nowait \
     -smp "${smp}" \
     -m 4096 \
     -cpu "${cpu}" \