x86/hvm: Rename hvm_emulate_init() and hvm_emulate_prepare() for clarity

x86/hvm: Rename hvm_emulate_init() and hvm_emulate_prepare() for clarity

 * Move hvm_emulate_init() to immediately after hvm_emulate_prepare(), as they
   are very closely related.
 * Rename hvm_emulate_prepare() to hvm_emulate_init_once() and
   hvm_emulate_init() to hvm_emulate_init_per_insn() to make it clearer how to
   and when to use them.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>