disp: msm: Subtract DSI interrupt count after interrupt was destroyed

DSI interrupt may be destroyed before it is disabled, it will cause to
the interrupt count can't be cleared, so subtrace DSI interrupt count
in disable function even it was destroyed.

Change-Id: I430b0281957db588c7405d5775d0c10f2f498b36
Signed-off-by: Lei Chen <chenlei@codeaurora.org>