x86/pv: Rename v->arch.pv_vcpu to v->arch.pv

x86/pv: Rename v->arch.pv_vcpu to v->arch.pv

The trailing _vcpu 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>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>