VPP-189 Fix 137 coverity no-op issues from vpeapigen

VPP-189 Fix 137 coverity no-op issues from vpeapigen

vpeapigen is not properly detecting no-op endian swap operations (on u8
or u8[] types) which in turn causes Coverity to currently report ~137
minor issues from the generated vpe.api.h file.

This patch makes vpeapigen comment out those no-op situations thus:

    /* a->interface_name[0..63] = a->interface_name[0..63] (no-op) */
    /* a->admin_up_down = a->admin_up_down (no-op) */

Change-Id: Ifbc5c93e1939206656e0515b528a4d167c539fd2
Signed-off-by: Chris Luke <chrisy@flirble.org>