crypto: ice: add stub bus scaling functions

Bus scaling might be disabled in the kernel configuration of
some platforms, in which case initialization will fail due
to the lack of bus scaling support.
Add stub functions to allow initialization without bus scaling.

Change-Id: Ib1edeac145ef1696e657f775cd938839b79dbac0
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>