vl.c: run preconfig loop before creating default RAM backend

vl.c: run preconfig loop before creating default RAM backend

Default RAM backend depends on numa_uses_legacy_mem(), which is
infulenced by -numa options on CLI or set-numa-node QMP command
at preconfig time. If QEMU is started with  '-preconfig'
without -numa, it will lead to creating default RAM backend
even if later set-numa-node is used to assing RAM to NUMA nodes
using 'memdev' NUMA option.
That at best will waste RAM object created by default and with
next patch adding a check to prevent usage of conflicting
 '-M memory-backend' and '-numa memdev'
options, it will make QEMU error out if user tries to configure
NUMA at preconfig time with memdev option, making set-numa-node
unusable.

To fix issue, move preconfig loop before default RAM backend is
created, so that numa_uses_legacy_mem() would take into account
effects of set-numa-node commands executed at preconfig time.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20200511141103.43768-2-imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>