sim: cris: do not pass cpu when writing memory during init

The point of passing down the cpu to core reads/writes is to signal which
cpu is making the access.  For system accesses (such as internal memory
initialization), passing the cpu down doesn't make sense, and in the case
of early init like cris, can cause crashes.  Since the cpu isn't fully set
up at this point, if the core code tries to access some fields (like the
PC reg), it'll crash.  While cris shouldn't be doing this setup here (it
should be in the inferior stage), we'll deal with that later.