KVM: MIPS: Add 64BIT capability

Add a new KVM_CAP_MIPS_64BIT capability to indicate that 64-bit MIPS
guests are available and supported. In this case it should still be
possible to run 32-bit guest code. If not available it won't be possible
to run 64-bit guest code and the instructions may not be available, or
the kernel may not support full context switching of 64-bit registers.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: linux-doc@vger.kernel.org
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 58ddedc..1e1a6c7 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -889,6 +889,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_IMMEDIATE_EXIT 136
 #define KVM_CAP_MIPS_VZ 137
 #define KVM_CAP_MIPS_TE 138
+#define KVM_CAP_MIPS_64BIT 139
 
 #ifdef KVM_CAP_IRQ_ROUTING