target/i386/kvm.c: Handle renaming of KVM_HINTS_DEDICATED

target/i386/kvm.c: Handle renaming of KVM_HINTS_DEDICATED

In kernel header commit 633711e8287, the define KVM_HINTS_DEDICATED
was renamed to KVM_HINTS_REALTIME. Work around this compatibility
break by (a) using the new constant name, and (b) defining it
if the headers don't.

Part (b) can be removed once we've updated our copy of the kernel
headers to a version that defines KVM_HINTS_REALTIME.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20180525132755.21839-5-peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>