arm/dt: msm8974: Configure spkdrv supply

The msm8974 CDP and Fluid have speaker drive which requires supply.
Configure speaker driver supply as an on demand so codec driver can
turn it on only when it's required.
Liquid has external supply which should be controlled by its ASoC machine
driver.  Configure Liquid's speaker driver supply with a dummy regulator
to make codec driver doesn't complain about lack of spkdrv supply.

Change-Id: I6c52920ab13e1a69d4ebdbf91b5365675d94fa4d
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>