hwc: Ensure yuvIndices doesn't exceed MAX_NUM_APP_LAYERS

* Fix a KW error arising out of
commit 036404772ff3d96a752e80d6a8bdbe1c305e39cf
* Ensure that yuvIndices array index doesn't exceed
MAX_NUM_APP_LAYERS

Change-Id: I331613b61530539e6b4c2b2029371f198695f519
1 file changed