arm/dt: msm8226: default to svs for cx/mx

Vote from regulator is not propagated to RPM because
the notification system does not receive the sleep vote
when it is cached. As a result of which, super turbo is
sent as the voltage during sleep by default. As a workaround default
to svs for cx and mx temporarily.

Change-Id: I5936059210953d32cd117917e4221d0f083dfe0a
Signed-off-by: Priyanka Mathur <pmathur@codeaurora.org>