xen: fix xen.h build for CONFIG_XEN_PVH=y

For CONFIG_XEN_PVH=y, xen.h uses bool before the type is known. Include
<linux/types.h> earlier.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20221123131057.3864183-1-jani.nikula@intel.com


Signed-off-by: Juergen Gross <jgross@suse.com>