A QemuOptsList can be of one of two kinds: either it is pre-validated, or
it accepts any key and validation happens somewhere else (typically in
a Visitor or against a list of QOM properties).  opts_accepts_any
returns true if a QemuOpts instance was created from a QemuOptsList of
the latter kind, but there is no function to do the check on a QemuOptsList.

Since this property comes from the QemuOptsList and almost all callers of
opts_accepts_any use opts->list anyway, modify the function to accept
QemuOptsList.

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>