prepare_mappings() uses the return value of map_private_vma() for the
size of the mapped vma. Unfortunately the return value of
map_private_vma() is an int, resulting in breakage when the size exceeds
31 bits. Change map_private_vma() to return only an error code, and
mutate addr in-place.
Signed-off-by: Jamie Liu <jamieliu@google.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>