Update kelvin renode script to properly support debugging

To debug Renode with GDB, the Renode simulation should be started by
GDB automatically when the debug server is attached to GDB. Clean up the
renode script to follow the same flow we used in springbok to make sure
GDB can capture the process reliably.

Change-Id: I416565bcb8b02b8b137fe2a7ebc822d9821607ac
diff --git a/kelvin.resc b/kelvin.resc
index 4a8aead..52c043a 100644
--- a/kelvin.resc
+++ b/kelvin.resc
@@ -41,7 +41,6 @@
 # get reliably triggered. We should probably root cause this later when we have
 # time, but as a workaround setting the breakpoint to reset_addr+4 instead seems
 # to work fine.
-$gdb_port?=3333
-machine StartGdbServer $gdb_port false sysbus.cpu2
 
-start
+# Enable vec_controlblock verbose logging
+logLevel -1 sysbus.vec_controlblock