clk: msm: clock-cpu-8996: Workaround a concurrent access bug

Limits Management hardware and the clock controller registers
cannot be accessed concurrently from two CPUs in the same
cluster. Provide mutual exclusion by using the scm_lmh_lock
mutex around the clock APIs that touch the CPU clock controller.

Change-Id: I74e6de7f35e46b3f841a4ac97dd5cf87cf0211a4
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>