msm: mdss: release ahb clocks when mdp clocks are released.

This change makes sure that all the clocks held by
the display driver gets disabled when the mdp clock
is also released and will switch the ahb vote to
active-only context, so the bus driver can also
free all the unneeded clocks when cpu is not active.

Change-Id: Id7ee92fdc6e5e91832e4dec61fb151ed20411ef1
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>