target/ppc: Handle NMI guest exit

target/ppc: Handle NMI guest exit

Memory error such as bit flips that cannot be corrected
by hardware are passed on to the kernel for handling.
If the memory address in error belongs to guest then
the guest kernel is responsible for taking suitable action.
Patch [1] enhances KVM to exit guest with exit reason
set to KVM_EXIT_NMI in such cases. This patch handles
KVM_EXIT_NMI exit.

[1] https://www.spinics.net/lists/kvm-ppc/msg12637.html
    (e20bbd3d and related commits)

Signed-off-by: Aravinda Prasad <[email protected]>
Signed-off-by: Ganesh Goudar <[email protected]>
Reviewed-by: David Gibson <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Message-Id: <20200130184423[email protected]>
[dwg: #ifdefs to fix compile for 32-bit target]
Signed-off-by: David Gibson <[email protected]>