ARM: dts: msm: enable HMP scheduling extensions via command line

SoCs sharing a common binary need the ability to individually turn HMP
scheduling extensions on or off. Make this a command line argument
that the bootloader can pick up from device tree.  SoCs that require
HMP scheduling need to explicitly enable it via the chosen node in
device tree. Currently MSM8994 and MSM8939 use HMP scheduling
extensions. Add the command line options to the device tree files for
these SoCs.

Change-Id: Idb24e6a72d6794154f73be2a693edc523c1cd241
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>