driver: thermal: lmh-dcvsh: Expose lmh frequency limit sysfs

LMH driver monitors for the LMH DCVSh throttling frequency and notifies
the scheduler. Expose this value via sysfs for the userspace to read the
limits frequency limit.

Change-Id: I59abdaf7ff702fc27667b1d4c350fe604f6bc4d5
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>