vmx: let opt_ept_ad always reflect the current setting

vmx: let opt_ept_ad always reflect the current setting

In case opt_ept_ad has not been set explicitly by the user via command
line or runtime parameter, it is treated as "no" on Avoton cpus.

Change that handling by setting opt_ept_ad to 0 for this cpu type
explicitly if no user value has been set.

By putting this into the (renamed) boot time initialization of vmcs.c
_vmx_cpu_up() can be made static.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>