xen: remove XEN_GUEST_HANDLE(ulong)

xen: remove XEN_GUEST_HANDLE(ulong)

Having both this handle (always unsigned long) and
XEN_GUEST_HANDLE(xen_ulong_t) (unsigned long on x86 and explicit size
of ARM) is confusing and error prone.

Replace the two remaining uses of the ulong handle, in grant set and
x86 set_gdt hypercalls, with xen_ulong_t.

This correctly sizes the grant frame entry as 64 bit on ARM but
leaves it as unsigned long on x86 (therefore no intended change on
x86). Likewise in set_gdt there is no actual change.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>