target-i386: Kill cpudef config section support

target-i386: Kill cpudef config section support

It's nice to have a flexible system to maintain CPU models as data, but
this is holding us from making improvements in the CPU code because it's
not using the common infra-structure, and because the machine-type data
is still inside C code.

Users who want to configure CPU features directly may simply use the
"-cpu" command-line option (and maybe an equivalent -device option in
the future) to set CPU features.

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>