ARM: dts: msm: Fix reg property for audio_ext_clk

This node is placed under the soc node, and that node has
address-cells and size-cells equal to 1. Thus reg property needs
two cells. Add a second cell indicating the size of the register
region. In this case it's just 4 bytes that are used in the
driver.

Change-Id: Ie3fca14a4712cbb95144206c2a1e28ef0cf7b6e9
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>