vl.c: numa_add(): Validate nodeid before using it

vl.c: numa_add(): Validate nodeid before using it

Without this check, QEMU will corrupt memory if a too-large nodeid is
provided in the command-line. e.g.:

  -numa node,mem=...,cpus=...,nodeid=65

This changes nodenr to unsigned long long, to avoid integer conversion
issues when converting the strtoull() result to int.

Signed-off-by: Eduardo Habkost <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Signed-off-by: Anthony Liguori <[email protected]>