xen: don't reload cr3 on suspend

It isn't necessary, and it makes the code needlessly non-portable.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>