sysemu/xen: Add missing 'exec/cpu-common.h' header for ram_addr_t type

As this header use the ram_addr_t type, it has to include
"exec/cpu-common.h" to avoid odd errors such:

  include/sysemu/xen.h:35:44: error: unknown type name 'ram_addr_t'; did you mean 'in_addr_t'?
   35 | static inline void xen_hvm_modified_memory(ram_addr_t start, ram_addr_t length)
      |                                            ^~~~~~~~~~
      |                                            in_addr_t

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200908155530.249806-4-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed