msm: limits: Add support for debug interface

Add support for a debug interface. The underlying
hardware interface can use this interface to register
the APIs required for debugging LMH.
These are the current debug interfaces that are
supported,

* /sys/debug/lmh_monitor/debug/data -> Interface to
    configure and read debug data from LMH hardware.
* /sys/debug/lmh_monitor/debug/data_types -> Reads
    the available datatypes that can be read from LMH
    hardware.
* /sys/debug/lmh_monitor/debug/config -> Interface to
    configure the LMH hardware.
* /sys/debug/lmh_monitor/debug/config_types -> Reads
    the available config types for the LMH hardware.

Change-Id: I1f81685bbde8fa770b4ca5a0154eaa9dccf484bf
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>