xen: replace XENFEAT_auto_translated_physmap with xen_pv_domain()

Instead of testing the XENFEAT_auto_translated_physmap feature, just
use !xen_pv_domain() which is equivalent.

This has the advantage that a kernel not built with CONFIG_XEN_PV
will be smaller due to dead code elimination.

Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20250826145608.10352-3-jgross@suse.com>