xenpaging: do not use DPRINTF/ERROR if xch handle is unavailable

xenpaging: do not use DPRINTF/ERROR if xch handle is unavailable

Fix DPRINTF/ERROR usage. Both macros reference a xch variable in local scope.
If xc_interface_open fails and after xc_interface_close, both can not be used
anymore. Use standard fprintf for this case.

Remove the code to print the exit value, its not really useful.
Its a left-over for debugging from an earlier patch.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>