kvm-all: Pass an error object to kvm_device_access

kvm-all: Pass an error object to kvm_device_access

In some circumstances, we don't want to abort if the
kvm_device_access fails. This will be the case during ITS
migration, in case the ITS table save/restore fails because
the guest did not program the vITS correctly. So let's pass an
error object to the function and return the ioctl value. New
callers will be able to make a decision upon this returned
value.

Existing callers pass &error_abort which will cause the
function to abort on failure.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Message-id: 1497023553-18411-2-git-send-email-eric.auger@redhat.com
[PMM: wrapped long line]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>