hdat: ignore zero length reserves
hdat: ignore zero length reserves

Hostboot can export reserved regions with a length of zero and these
should be ignored rather than being turned into reserved range. While
we're here fix a memory leak by moving the "too large" region check
to before we allocate space for the label.

Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

open-power/skiboot,stewart-ibm/skiboot,mikey/skiboot,stewart-ibm/skiboot,shenki/skiboot,qemu/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,mikey/skiboot,mikey/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,stewart-ibm/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot