arm/virt: Use PSCI v0.2 function IDs in the DT when KVM uses PSCI v0.2

The current code supplies the PSCI v0.1 function IDs in the DT even when
KVM uses PSCI v0.2.

This will break guest kernels that only support PSCI v0.1 as they will
use the IDs provided in the DT.  Guest kernels with PSCI v0.2 support
are not affected by this patch, because they ignore the function IDs in
the device tree and rely on the architecture definition.

Define QEMU versions of the constants and check that they correspond to
the Linux defines on Linux build hosts.  After this patch, both guest
kernels with PSCI v0.1 support and guest kernels with PSCI v0.2 should
work.

Tested on TC2 for 32-bit and APM Mustang for 64-bit (aarch64 guest
only).  Both cases tested with 3.14 and linus/master and verified I
could bring up 2 cpus with both guest kernels.  Also tested 32-bit with
a 3.14 host kernel with only PSCI v0.1 and both guests booted here as
well.

Cc: qemu-stable@nongnu.org
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>