ARM: dts: msm: specify ADC channel for TEMP_ALARM device on PMXPRAIRIE PMIC

Specify the PMIC DIE_TEMP ADC channel for the TEMP_ALARM PMIC
peripheral device found in the PMXPRAIRIE PMIC.  This ensures
that clients can read the exact die temperature of this PMIC
at runtime instead of relying upon a very coarse estimate based
upon the over-temperature stage.

Change-Id: I2813d2c6b11825b8a8b685dbcf3051841b65031c
Signed-off-by: David Collins <collinsd@codeaurora.org>