libxl: ARM build: fix type of libxl__srm_callout_callback_restore_results

libxl: ARM build: fix type of libxl__srm_callout_callback_restore_results

COLO introduced a few callbacks. The original implementation used
unsigned long for a type which in fact should be xen_pfn_t. That broke
libxl compilation on ARM, because xen_pfn_t is not a synonym for
unsigned long on ARM platform.

Fixing this requires modifying the perl script: specifically now we
need to include xenctrl.h before _libxl_save_msgs_*.h, rather than
afterwards, so that we can use xen_pfn_t there.

Reported-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>