x86/vmx: Drop ept_get_*() helpers

x86/vmx: Drop ept_get_*() helpers

The ept_get_*() helpers are not used consistently, and are more verbose than
the code they wrap.  Drop the wrappers and use the internal union names
consistently.

While making these adjustments, drop the redundant ept_* prefix from mt, wl
and ad, and rename the asr field to mfn for consistency with Xen's existing
terminology.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Kevin Tian <kevin.tian@intel.com>