ppc: Fix coding style in op_helper.c

op_helper.c will be split by the next patches, fix
style issues before that.
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NAlexander Graf <agraf@suse.de>