msm: camera: Ignore composite done irq 3

In dual vfe usecase, composite done irq 3 is reserved
for microcontroller to trigger scaler configuration
update. Microcontroller will read and clear the mask.
By ignoring the irq from VFE side, we avoid a race
condition where VFE clear the mask before microcontroler
read it and miss scaler configuration.

Change-Id: Iae934915e0c29c8fe6a87d6c066572165eab3512
Signed-off-by: Kevin Chan <ktchan@codeaurora.org>