Model names were mapped 1:1 to type names. As a side effect this
registered a type "any", which is now a device.
To avoid "-device any" silliness and to pave the way for compiling
multiple targets into one executable, adopt a <name>-<arch>-cpu scheme.
No functional changes for -cpu arguments or -cpu ? output.
Signed-off-by: Andreas Färber <afaerber@suse.de>