PPC: Fix rldcl

The implementation for rldcl tried to always fetch its
parameters from the opcode, even though the opcode was
already passed in in decoded and different forms.

Use the parameters instead, fixing rldcl.

Reported-by: Torbjorn Granlund <tg@gmplib.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Alexander Graf <agraf@suse.de>