[vectorIntrinsics] Benchmark related fixes

[Viswanathan, Sandhya]

Please find below a webrev which fixes two failures observed while running benchmarks:
http://cr.openjdk.java.net/~sviswanathan/vectorIntrinsics/Benchfix/wenrev.00/


  1.  ChaChaBench: java.lang.UnsupportedOperationException: ROL: operator is not implemented

The fix is in the Vector API Java implementation: Call opcode() after handling operators like ROL/ROR etc.

  1.  ByteScalar.gather/scatter: java.lang.ArrayIndexOutOfBoundsException: Index 1071 out of bounds for length 1024

The fix is in the scalar benchmarks adjusting the index value to not go out of bounds.

Best Regards,
Sandhya
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