Add 8-bit support to TABLE

It is challenging to work back from the RESCALE->TABLE->RESCALE
for a simple 8-bit lookup. This adds support to TOSA for a
simple direct 256 entry 8-bit lookup table for the TABLE operator.

The 16-bit interpolated table is still required for a conformant
implementation.

Change-Id: I0ef218444f0b57b880aa8d1c7e96efedae72eb53
Signed-off-by: Eric Kunze <eric.kunze@arm.com>