msm: thermal: Define no limit for frequency request

During probe time, if driver sees that the rail is frequency
request, then assign MSM_CPUFREQ_NO_LIMIT as min level which
is used to relax voltage restriction.

Change-Id: Ib33e2501b19b121f66bd8ad2b49a49986ba70f59
CRs-Fixed: 462816
Signed-off-by: Jennifer Liu <chihning@codeaurora.org>