exec.c: Allow target CPUs to define multiple AddressSpaces

Allow multiple calls to cpu_address_space_init(); each
call adds an entry to the cpu->ases array at the specified
index. It is up to the target-specific CPU code to actually use
these extra address spaces.

Since this multiple AddressSpace support won't work with
KVM, add an assertion to avoid confusing failures.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

cpus.c

@@ -1375,6 +1375,7 @@ void qemu_init_vcpu(CPUState *cpu)
         /* If the target cpu hasn't set up any address spaces itself,
          * give it the default one.
          */
+        cpu->num_ases = 1;
         cpu_address_space_init(cpu, &address_space_memory, 0);
     }