x86/xen: use correct types for addresses in arch/x86/xen/setup.c

In many places in arch/x86/xen/setup.c wrong types are used for
physical addresses (u64 or unsigned long long). Use phys_addr_t
instead.

Use macros already defined instead of open coding them.

Correct some other type mismatches.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>