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

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

This reverts commit 1b36e4f5a5de585210ea95f2257839c2312be28f.

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>