KVM: selftests: Drop stale function parameter comment for nested_map()

nested_map() does not take a parameter named eptp_memslot. Drop the
comment referring to it.
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220520233249.3776001-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/lib/x86_64/vmx.c

@@ -486,7 +486,6 @@ void nested_pg_map(struct vmx_pages *vmx, struct kvm_vm *vm,
  *   nested_paddr - Nested guest physical address to map
  *   paddr - VM Physical Address
  *   size - The size of the range to map
- *   eptp_memslot - Memory region slot for new virtual translation tables
  *
  * Output Args: None
  *