msm: mdss: Fill irq information correctly for dsi 6G

For DSI 6G fill the irq information at correct place so as
to avoid the crash and also call irq disable soon after
requesting for irq.

Change-Id: Icbf6f24fc6d938f1943f124f3d7368187743b36d
Signed-off-by: Shivaraj Shetty <shivaraj@codeaurora.org>