ARM: dts: msm8916: update reg property in the cpu nodes

Update the reg property to contain one address cell instead
of two as MSM8916 has only 4 cpus and does not require more
than a single cell to represent cpus in device tree.

Change-Id: Ic3d34a200a3c8093957d3c0234b323e518550d72
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>