msm: lpm-levels: Allow clock gating even when sleep_disabled is set

The system can boot with all low power modes disabled by setting
sleep_disabled. In this scenario clock gating would also be disabled.
This could lead to thermal conditions that would result in the cores
being hotplugged. Even in the case where all other low power modes are
disabled allow the system to select clock gating as the default level.

Change-Id: I9460dbb417947987a8519813f98ac68de36ba538
Signed-off-by: Karthik Parsha <kparsha@codeaurora.org>