This actually covers two different sections of the encoding table:

   Advanced SIMD scalar two-register miscellaneous FP16
   Advanced SIMD two-register miscellaneous (FP16)

The difference between the two is covered by a combination of Q (bit
30) and S (bit 28). Notably the FRINTx instructions are only
available in the vector form.

This is just the decode skeleton which will be filled out by later
patches.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20180227143852.11175-17-alex.bennee@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>