Fixes to pass NEGATE op test.

- Elementwise unary op input/output type should match.
- TOSA_UNPREDICTABLE should ONLY be sent when a tensor with negative dimension is read/written

Signed-off-by: Kevin Cheng <kevin.cheng@arm.com>
Change-Id: I689518933a2b56cd62793e3f28ea66a6e57b057c