Fix condition in mutateOperationOperandTypeSkip for conv ops.

The filter tensor is not always operand 1 if there are multiple
operations in the model.

Test: 1.2 VTS tests with sample driver
Change-Id: I8925dfd18072ae5579657e8aa13128e7d9f58324
Merged-In: I8925dfd18072ae5579657e8aa13128e7d9f58324
(cherry picked from commit 8804423c)