ARM: dts: msm: use hardware default BMD on pmi8994 charger

Currently there are two variants of pmi8994 released with different
hardware defaults for battery presence detection. It is more desirable
to use these defaults so that the behavior of the device pre-linux boot
and post linux boot are consistent.

Remove the qcom,bmd-pin-src property to allow the driver to use the
hardware defaults.

Change-Id: Id285745a0891892e39542a80e295cf6b646f3b0a
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>