msm: clock-local2: Don't assume a branch's parent is a local RCG

Starting with the 8974, it is possible to have rate-settable
branches that don't have a locally controlled RCG as their
parents. Fix branch_clk_list_rate to not make this assumption.

Change-Id: I99bd4506cd3deb62b0180c7558112b148570d682
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>