xen: Convert page_to_mfn and mfn_to_page to use typesafe MFN

xen: Convert page_to_mfn and mfn_to_page to use typesafe MFN

Most of the users of page_to_mfn and mfn_to_page are either overriding
the macros to make them work with mfn_t or use mfn_x/_mfn because the
rest of the function use mfn_t.

So make page_to_mfn and mfn_to_page return mfn_t by default. The __*
version are now dropped as this patch will convert all the remaining
non-typesafe callers.

Only reasonable clean-ups are done in this patch. The rest will use
_mfn/mfn_x for the time being.

Lastly, domain_page_to_mfn is also converted to use mfn_t given that
most of the callers are now switched to _mfn(domain_page_to_mfn(...)).

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>