common/memory: fix an XSM error path

common/memory: fix an XSM error path

XENMEM_{in,de}crease_reservation as well as XENMEM_populate_physmap
return the extent at which failure was detected, not error indicators.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Tim Deegan <tim@xen.org>
master commit: 76d4ff26d9647088353acaf4a56388a354a5d6e9
master date: 2015-01-19 11:59:05 +0100