msm: mdss: only release mdp dsi clock when reset

Earlier, we were releasing all the MDP clocks at
kernel transition.  We only need to release
the mdp dsi clock.

Change-Id: Iafa43afc1194e5f7cb50445a9542a21b16ffaef5
Signed-off-by: Xiaoming Zhou <zhoux@codeaurora.org>