xen/hvm: Rename d->arch.hvm_domain to d->arch.hvm

xen/hvm: Rename d->arch.hvm_domain to d->arch.hvm

The trailing _domain suffix is redundant, but adds to code volume.  Drop it.

Reflow lines as appropriate, and switch to using the new XFREE/etc wrappers
where applicable.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>