sim: cr16: add ifdefs around undefined syscalls

sim: cr16: add ifdefs around undefined syscalls

The cr16 libgloss port does not define these syscall numbers, so trying
to use them results in build failures [1].  The cr16 code already uses
ifdefs around a bunch of syscalls, so extend that style to cover the
ones that are currently missing.  Now we can at least compile.

[1] http://sourceware.org/ml/gdb-patches/2011-06/msg00118.html
Signed-off-by: Mike Frysinger <vapier@gentoo.org>