numa: clarify error message when node index is out of range in -numa dist, ...

numa: clarify error message when node index is out of range in -numa dist, ...

When using following CLI:
  -numa dist,src=128,dst=1,val=20
user gets a rather confusing error message:
   "Invalid node 128, max possible could be 128"

Where 128 is number of nodes that QEMU supports (MAX_NODES),
while src/dst is an index up to that limit, so it should be
MAX_NODES - 1 in error message.
Make error message to explicitly state valid range for node
index to be more clear.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1526483174-169008-1-git-send-email-imammedo@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>