OMAP4: hwmod: Introduce the module control in hwmod control

Take advantage of the explicit modulemode control to fix
the way parents clocks are managed.
A module must be disabled before any parents are disabled.
That programming model was not possible with the previous
implementation that was considering a modulemode as a leaf
clock node managed by the clock fmwk.
This was leading to bad crash upon disable when the parent
clock was gated before the module completed its transition
to idle.

Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>