When compiling Qemu with older kernel headers, the PVR setting
mechanism isn't available yet. Unfortunately, back then I didn't add
a capability we could check against, so all we can do is add a configure
test to see if we support PVR setting. For BookE, we don't care yet.

This fixes compilation errors with KVM enabled on older kernel headers
(like 2.6.32).
Signed-off-by: NAlexander Graf <agraf@suse.de>