ARM: dts: msm: fix avtimer clk-div property usage in all targets

In 8937 target, avtimer values are not coming proper.
since clk-div property is not defined correctly,
driver is not able to parse the value from device tree.
Update the property name clk-div so that it is
parsed by driver.

Change-Id: Ieda475d75792b108f357ba2ae9b2e6168158f1cd
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>