ARM: dts: msm: specify ADC channel for PMA8084 temperature alarm peripheral

Add a qcom,channel-num property to the PMA8084 temperature
alarm peripheral device with a value which corresponds to the
PMIC die temperature ADC channel.  This allows the temperature
alarm device to report the real-time die temperature instead of
an estimate.

Change-Id: I198b84aded411da8bb6a44b89b7339b8e7482d98
Signed-off-by: David Collins <collinsd@codeaurora.org>