stm32f205: Fix SoC type name

The type name for the SoC device, unlike those of its sub-devices,
did not follow the QOM naming conventions. While the usage is internal
only, this is exposed through QMP and HMP, so fix it before release.

Cc: Alistair Francis <alistair.francis@xilinx.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Alistair Francis <alistair@alistair23.me>
Message-id: 1428676676-23056-1-git-send-email-afaerber@suse.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>