msm: clock-local2: Introduce a static mux clock

MSM clock controllers contain static muxes that select
between clock sources without placing constraints on the
state of the sources. Introduce a clock and ops that provide
functionality to configure and control these static muxes.

Change-Id: Iaf0d6975b1a4c3db22923850196a0e603e5cb5a6
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>