regulator: core: add debugfs regulator monitoring and control features

Add several debugfs files for each registered regulator which
allow for monitoring of the regulator state and the requests from
each consumer.  Also configure these files as writeable so that a
debug consumer requested per-regulator can easily vote on the
regulator state.

This commit is a squash of the following msm-4.4 branch commits
with checkpatch warnings and other minor issues resolved:

commit 32c846e998a1 ("regulator: debugfs: Adding debugfs
                      functions into regulator framework")
commit db58e9bdc318 ("regulator: core: fix regulator bypass
                      logic")
commit 40456168dbe8 ("regulator: core: put debugfs consumer
                      handle when unregistering a regulator")
commit a118e09f3ce4 ("regulator: core: correct double remove
                      in rdev_deinit_debugfs")
commit 7ff3a4cc82e7 ("regulator: correct name used in debug
                      consumer regulator_get call")

Change-Id: Ia13b8f698868374499bb9be390ade4519c517e29
Signed-off-by: David Collins <collinsd@codeaurora.org>