ARM: dts: qcom: Remove extra reg element from iadc device

This doesn't match the binding, and the driver doesn't look to
be using it. Remove the extra element.

CC: Ivan T. Ivanov <ivan.ivanov@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Ivan T. Ivanov <ivan.ivanov@linaro.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>