KVM: fix cpuid E2BIG handling for extended request types

(cherry picked from commit cb007648)

If we run out of cpuid entries for extended request types
we should return -E2BIG, just like we do for the standard
request types.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>