This fixes commit 81c4d8a3.

Before the commit above, we always used to obtain information about the
current OPP from hardware. If this performance level was different from
the one we wanted to set, we would go ahead and set it. But after this
patch, we use a cached value for the current opp which (somehow) ends up
being different from what hardware has knowledge of. This results in
an opp change request sometimes failing.