Revert "cpu: Move cpu_common_props to hw/core/cpu.c"

This reverts commit 1b36e4f5a5.

Despite a comment saying why cpu_common_props cannot be placed in
a file that is compiled once, it was moved anyway.  Revert that.

Since then, Property is not defined in hw/core/cpu.h, so it is now
easier to declare a function to install the properties rather than
the Property array itself.

Cc: Eduardo Habkost <ehabkost@redhat.com>
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/hw/core/cpu.h

@@ -1008,6 +1008,7 @@ void QEMU_NORETURN cpu_abort(CPUState *cpu, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
 
 /* $(top_srcdir)/cpu.c */
+void cpu_class_init_props(DeviceClass *dc);
 void cpu_exec_initfn(CPUState *cpu);
 void cpu_exec_realizefn(CPUState *cpu, Error **errp);
 void cpu_exec_unrealizefn(CPUState *cpu);