KVM: struct kvm_memory_slot.id -> short

We're currently offering a whopping 32 memory slots to user space, an
int is a bit excessive for storing this.  We would like to increase
our memslots, but SHRT_MAX should be more than enough.

Reviewed-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fec6075..32fdc45 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -270,7 +270,7 @@
 	struct kvm_arch_memory_slot arch;
 	unsigned long userspace_addr;
 	u32 flags;
-	int id;
+	short id;
 	bool user_alloc;
 };
 
@@ -330,7 +330,7 @@
 	u64 generation;
 	struct kvm_memory_slot memslots[KVM_MEM_SLOTS_NUM];
 	/* The mapping table from slot id to the index in memslots[]. */
-	int id_to_index[KVM_MEM_SLOTS_NUM];
+	short id_to_index[KVM_MEM_SLOTS_NUM];
 };
 
 struct kvm {