COMPMID-421: Added FP16 support to Arithmetic Subtraction.

Change-Id: I2043531e8e81f28354a208ff91024c3954389422
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/80304
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
3 files changed