VMX: remove the problematic set_uc_mode logic

VMX: remove the problematic set_uc_mode logic

XSA-60 security hole comes from the problematic vmx_set_uc_mode.
This patch remove vmx_set_uc_mode logic, which will be replaced by
PAT approach at later patch.

This is CVE-2013-2212 / XSA-60.

Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>
Acked-by: Jun Nakajima <jun.nakajima@intel.com>