KVM: x86: Fix warning due to implicit truncation on 32-bit KVM

Explicitly cast the integer literal to an unsigned long when stuffing a
non-canonical value into the host virtual address during private memslot
deletion.  The explicit cast fixes a warning that gets promoted to an
error when running with KVM's newfangled -Werror setting.

  arch/x86/kvm/x86.c:9739:9: error: large integer implicitly truncated
  to unsigned type [-Werror=overflow]

Fixes: a3e967c0b87d3 ("KVM: Terminate memslot walks via used_slots"
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -9735,8 +9735,12 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
 		if (!slot || !slot->npages)
 			return 0;
 
-		/* Stuff a non-canonical value to catch use-after-delete. */
-		hva = 0xdeadull << 48;
+		/*
+		 * Stuff a non-canonical value to catch use-after-delete.  This
+		 * ends up being 0 on 32-bit KVM, but there's no better
+		 * alternative.
+		 */
+		hva = (unsigned long)(0xdeadull << 48);
 		old_npages = slot->npages;
 	}