Add instructions of SR opcode format.
Add micro-op generator functions for saturate.
Add helper return from exception (rfe).

Signed-off-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Message-id: 1409572800-4116-16-git-send-email-kbastian@mail.uni-paderborn.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>