ARM: dts: msm: Add regulator references in msm bus devices for sm8150

In order to be able to vote on MMCX regulator during the sequence of
connecting and disconnecting multimedia slaves, add new node specific
regulator references.

Change-Id: I7c96a5ee639c2a330b3e6787a4fe8ce1dd81c40b
Signed-off-by: David Dai <daidavid1@codeaurora.org>