Since commit b35ba30f when it was introduced, phys_page_compact()
takes an unused compacted argument.

ubsan complains about it when launching qemu-x86_64 without arguments:
qemu/exec.c:310:5: runtime error: variable length array bound evaluates to non-positive value 0

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>