drivers: lmh-dcvsh: Add debug support

LMH DCVSh hardware can provide debug information. Provide a generic
debugfs interface in LMH DCVSh driver to support querying the
hardware for different information using a different command formats.

Change-Id: I10053a224e79f549ec68f9c39d652e7668b34ffc
Signed-off-by: Ram Chandrasekar <rkumbako@codeaurora.org>