display/sm501 display/ati: Fix to realize "i2c-ddc"

display/sm501 display/ati: Fix to realize "i2c-ddc"

sm501_init() and ati_vga_realize() create an "i2c-ddc" device, but
neglect to realize it.  Affects machines sam460ex, shix, r2d, and
fulong2e.

In theory, a device becomes real only on realize.  In practice, the
transition from unreal to real is a fuzzy one.  The work to make a
device real can be spread between realize methods (fine),
instance_init methods (wrong), and board code wiring up the device
(fine as long as it effectively happens on realize).  Depending on
what exactly is done where, a device can work even when we neglect
to realize it.

This one appears to work.  Nevertheless, it's a clear misuse of the
interface.  Even when it works today (more or less by chance), it can
break tomorrow.

Fix by realizing it right away.  Visible in "info qom-tree"; here's
the change for sam460ex:

     /machine (sam460ex-machine)
       [...]
       /unattached (container)
         [...]
    -    /device[14] (sii3112)
    +    /device[14] (i2c-ddc)
    +    /device[15] (sii3112)
         [rest of device[*] renumbered...]

Fixes: 4a1f253adb45ac6019971193d5077c4d5d55886a
Fixes: c82c7336de58876862e6b4dccbda29e9240fd388
Cc: BALATON Zoltan <balaton@eik.bme.hu>
Cc: qemu-ppc@nongnu.org
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Philippe Mathieu-Daudé <f4bug@amsat.org>
Cc: Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Tested-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200609122339.937862-19-armbru@redhat.com>