[AArch64] PR target/20553, fix opcode mask for SIMD multiply by element

[Nick Clifton]

Hi Jiong,

> opcode/
> 2016-09-27  Jiong Wang  <jiong.wang@arm.com>
> 
>         * aarch64-tbl.h (fmla, fmls, fmul, fmulx): Fix opcode mask field.
> 
> gas/
> 2016-09-27  Jiong Wang  <jiong.wang@arm.com>
> 
>         * testsuite/gas/aarch64/advsimd-fp16.s (indexed_elem): New high index
>         testcases for H and S variants.  New low index testcases for D variant.
>         * testsuite/gas/aarch64/advsimd-fp16.d: Update expected results.

Approved - please apply.

Cheers
  Nick