KVM: PPC: Book3S PR: Handle Facility interrupt and FSCR

POWER8 introduced a new interrupt type called "Facility unavailable interrupt"
which contains its status message in a new register called FSCR.

Handle these exits and try to emulate instructions for unhandled facilities.
Follow-on patches enable KVM to expose specific facilities into the guest.

Signed-off-by: Alexander Graf <agraf@suse.de>

---

v1 -> v2:

  - Only emulate instructions in !PR guest mode
KVM: PPC: Book3S PR: Expose TAR facility to guest

POWER8 implements a new register called TAR. This register has to be
enabled in FSCR and then from KVM's point of view is mere storage.

This patch enables the guest to use TAR.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S PR: Expose EBB registers

POWER8 introduces a new facility called the "Event Based Branch" facility.
It contains of a few registers that indicate where a guest should branch to
when a defined event occurs and it's in PR mode.

We don't want to really enable EBB as it will create a big mess with !PR guest
mode while hardware is in PR and we don't really emulate the PMU anyway.

So instead, let's just leave it at emulation of all its registers.

Signed-off-by: Alexander Graf <agraf@suse.de>
KVM: PPC: Book3S PR: Expose TM registers

POWER8 introduces transactional memory which brings along a number of new
registers and MSR bits.

Implementing all of those is a pretty big headache, so for now let's at least
emulate enough to make Linux's context switching code happy.

Signed-off-by: Alexander Graf <agraf@suse.de>