ARM: dts: msm: use external sense on msm-pmi8994

PMI8994 devices will be enabling parallel charging. An external sense
resistor is needed to capture the current going through the parallel
charger.

Select the external sense in advance to prevent any issues with parallel
charging configuration.

Change-Id: I2e468aa9526f51c8eee3de492cd0d36abb5c3df6
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>