hw/intc/xics: Include missing 'cpu.h' header

Include missing headers in order to avoid when refactoring
unrelated headers:

  hw/intc/xics.c: In function 'icp_realize':
  hw/intc/xics.c:304:5: error: unknown type name 'PowerPCCPU'
    304 |     PowerPCCPU *cpu;
        |     ^~~~~~~~~~

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
1 file changed