msm: lpm_levels: Allow hotplug even if the driver hasn't been probed.

When the system runs into a thermal condition, the kernel thermal module
tries to hotplug the core before lpm probe is initialized. If lpm probe
isn't initialized the power collapse modes are not chosen for hotplug and
the thermal condition isn't mitigated resulting in a thermal reset. Fix
issue by choosing the deepest sleep mode for a given cpu.

CRs-fixed:609769
Change-Id: I4f724ba4f682c640ffde5686b8e194a4de6808f8
Signed-off-by: Mahesh Sivasubramanian <msivasub@codeaurora.org>
(cherry picked from commit 6e342027)