softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()

When adding RAM_NORESERVE, we forgot to remove the old assertion when
adding the updated one, most probably when reworking the patches or
rebasing. We can easily crash QEMU by adding
  -object memory-backend-ram,id=mem0,size=500G,reserve=off
to the QEMU cmdline:
  qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
  Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
  == 0' failed.

Fix it by removing the old assertion.

Fixes: 8dbe22c6 ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-id: 20210805092350.31195-1-david@redhat.com
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>