msm: camera: isp: Fix composite stats irq handling

If more than one stats irq are composite together, callback for both
stats should be sent only after composite stats irq is received.
Currently there is a bug due to which stats callback was called
even if one of the stats irq that is part of composite is received.
Fix bug by handling composite and non composite irq separately.

Change-Id: I8cd0c857ff6c8271e450ee3ecc2eaa3cf2866508
Signed-off-by: Sreesudhan Ramakrish Ramkumar <srramku@codeaurora.org>