KVM: add hypercall nr to kvm_run

Add the hypercall number to kvm_run and initialize it.  This changes the ABI,
but as this particular ABI was unusable before this no users are affected.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

include/linux/kvm.h

@@ -99,6 +99,7 @@ struct kvm_run {
 		} mmio;
 		/* KVM_EXIT_HYPERCALL */
 		struct {
+			__u64 nr;
 			__u64 args[6];
 			__u64 ret;
 			__u32 longmode;