MIPS: MIPSsim: Fix build error if MSC01E_INT_BASE is undefined.

This fixes kernel.org bugzilla 13595, see
http://bugzilla.kernel.org/show_bug.cgi?id=13595



Reported-by:  <dvice_null@yahoo.com>

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>