This patch adds general support that will be used by the VSX helper
routines:

  - a union describing the various VSR subfields.
  - access routines to get and set VSRs
  - VSX decoders
  - a general routine to generate a handler that invokes a VSX
    helper.
Signed-off-by: NTom Musta <tommusta@gmail.com>
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NAlexander Graf <agraf@suse.de>