ARM: dts: msm: Add A7 subsystem clocks for MSM ZIRC

A7 subsystem contains a cpu clock PLL and a cpu clock.
Add their data in device tree to define these clocks.
Also, add a A7 measurement clock to allow measuring
the A7 cpu clock.

Change-Id: Ie991abc7fde5ada22eb9cc39fdaa39ed41bf5a37
Signed-off-by: Tianyi Gou <tgou@codeaurora.org>