ARM: dts: msm: Add CPU / L2 clock control nodes for 8992

Add the CPU ACC and L2 clock control nodes to the 8992
device tree, and configure the CPU nodes to refer to their
corresponding ACC / L2 nodes to allow booting the secondary
CPUs using the full boot chain.

Change-Id: I24a469614d8e1ac9f0909abe271fc162face7192
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>