msm: clock-local: Don't set N val when not using mn counter

If the mn counter isn't being used we can skip setting the n
value bits. Do this so that clock handoff works when an mn
counter isn't being used and to avoid setting bits when they have
no effect.

Change-Id: I12afbd07928bcc08128941bfc0a0bdfe6771caa6
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>