This patch adds the Vector SHA Sigma instructions introduced in Power
ISA Version 2.07:

  - Vector SHA-512 Sigma Doubleword (vshasigmad)
  - Vector SHA-256 Sigma Word (vshasigmaw)
Signed-off-by: NTom Musta <tommusta@gmail.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>