xen: remove tmem from hypervisor

xen: remove tmem from hypervisor

This patch removes all tmem related code and CONFIG_TMEM from the
hypervisor. Also remove tmem hypercalls from the default XSM policy.

It is written as if tmem is disabled and tmem freeable pages is 0.

We will need to keep public/tmem.h around forever to avoid breaking
guests.  Remove the hypervisor only part and put guest visible part
under a xen version check. Take the chance to remove trailing
whitespaces.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>