msm: mdss: fix mdp3 core clock active in doze mode issue

Mdp3 core clock was not getting turned off in doze mode because
vsync interrupt ref count were not balanced. This was preventing the
interrupt disabling during the idle screen and keeping mdp3 core clock
ON in doze mode.
Fix is increase per interrupt ref counting only if interrupt disabled else
don't update ref count. This helps in keeping the ref count balanced.

Change-Id: I5edc80475c810f65bf00ac9d5483a58fb284d5ae
Signed-off-by: Sachin Bhayare <sachin.bhayare@codeaurora.org>