KVM: PPC: booke: Add watchdog emulation

KVM: PPC: booke: Add watchdog emulation

This patch adds the watchdog emulation in KVM. The watchdog
emulation is enabled by KVM_ENABLE_CAP(KVM_CAP_PPC_BOOKE_WATCHDOG) ioctl.
The kernel timer are used for watchdog emulation and emulates
h/w watchdog state machine. On watchdog timer expiry, it exit to QEMU
if TCR.WRC is non ZERO. QEMU can reset/shutdown etc depending upon how
it is configured.

Signed-off-by: Liu Yu <[email protected]>
Signed-off-by: Scott Wood <[email protected]>
[[email protected]: reworked patch]
Signed-off-by: Bharat Bhushan <[email protected]>
[agraf: adjust to new request framework]
Signed-off-by: Alexander Graf <[email protected]>