OMAP clockdomain: initialize clockdomain registers when the clockdomain layer starts

When the clockdomain layer initializes, place all clockdomains into
software-supervised mode, and clear all wakeup and sleep dependencies
immediately, rather than waiting for the PM code to do this later.
This fixes a major bug where critical sleep dependencies added by the
hwmod code are cleared during late PM init.

As a side benefit, the _init_{wk,sleep}dep_usecount() functions are no
longer needed, so remove them.

Kevin Hilman <khilman@deeprootsystems.com> did all the really hard work on
this, identifying the problem and finding the bug.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>